BASH_BUILTINS(1) General Commands Manual BASH_BUILTINS(1) NNAAMMEE :, ., [, alias, bg, bind, break, builtin, caller, cd, command, compgen, complete, compopt, continue, declare, dirs, disown, echo, enable, eval, exec, exit, export, false, fc, fg, getopts, hash, help, history, jobs, kill, let, local, logout, mapfile, popd, printf, pushd, pwd, read, readarray, readonly, return, set, shift, shopt, source, suspend, test, times, trap, true, type, typeset, ulimit, umask, unalias, unset, wait - bash built-in commands, see bbaasshh(1) BBAASSHH BBUUIILLTTIINN CCOOMMMMAANNDDSS Unless otherwise noted, each builtin command documented in this section as accepting options preceded by -- accepts ---- to signify the end of the options. The ::, ttrruuee, ffaallssee, and tteesstt/[[ builtins do not accept options and do not treat ---- specially. The eexxiitt, llooggoouutt, rreettuurrnn, bbrreeaakk, ccoonn-- ttiinnuuee, lleett, and sshhiifftt builtins accept and process arguments beginning with -- without requiring ----. Other builtins that accept arguments but are not specified as accepting options interpret arguments beginning with -- as invalid options and require ---- to prevent this interpreta- tion. :: [_a_r_g_u_m_e_n_t_s] No effect; the command does nothing beyond expanding _a_r_g_u_m_e_n_t_s and performing any specified redirections. The return status is zero. .. _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s] ssoouurrccee _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s] Read and execute commands from _f_i_l_e_n_a_m_e in the current shell en- vironment and return the exit status of the last command exe- cuted from _f_i_l_e_n_a_m_e. If _f_i_l_e_n_a_m_e does not contain a slash, filenames in PPAATTHH are used to find the directory containing _f_i_l_e_n_a_m_e, but _f_i_l_e_n_a_m_e does not need to be executable. The file searched for in PPAATTHH need not be executable. When bbaasshh is not in _p_o_s_i_x _m_o_d_e, it searches the current directory if no file is found in PPAATTHH. If the ssoouurrcceeppaatthh option to the sshhoopptt builtin command is turned off, the PPAATTHH is not searched. If any _a_r_g_u_- _m_e_n_t_s are supplied, they become the positional parameters when _f_i_l_e_n_a_m_e is executed. Otherwise the positional parameters are unchanged. If the --TT option is enabled, .. inherits any trap on DDEEBBUUGG; if it is not, any DDEEBBUUGG trap string is saved and restored around the call to .., and .. unsets the DDEEBBUUGG trap while it exe- cutes. If --TT is not set, and the sourced file changes the DDEEBBUUGG trap, the new value is retained when .. completes. The return status is the status of the last command exited within the script (0 if no commands are executed), and false if _f_i_l_e_n_a_m_e is not found or cannot be read. aalliiaass [--pp] [_n_a_m_e[=_v_a_l_u_e] ...] AAlliiaass with no arguments or with the --pp option prints the list of aliases in the form aalliiaass _n_a_m_e=_v_a_l_u_e on standard output. When arguments are supplied, an alias is defined for each _n_a_m_e whose _v_a_l_u_e is given. A trailing space in _v_a_l_u_e causes the next word to be checked for alias substitution when the alias is expanded. For each _n_a_m_e in the argument list for which no _v_a_l_u_e is sup- plied, the name and value of the alias is printed. AAlliiaass re- turns true unless a _n_a_m_e is given for which no alias has been defined. bbgg [_j_o_b_s_p_e_c ...] Resume each suspended job _j_o_b_s_p_e_c in the background, as if it had been started with &&. If _j_o_b_s_p_e_c is not present, the shell's notion of the _c_u_r_r_e_n_t _j_o_b is used. bbgg _j_o_b_s_p_e_c returns 0 unless run when job control is disabled or, when run with job control enabled, any specified _j_o_b_s_p_e_c was not found or was started without job control. bbiinndd [--mm _k_e_y_m_a_p] [--llppssvvPPSSVVXX] bbiinndd [--mm _k_e_y_m_a_p] [--qq _f_u_n_c_t_i_o_n] [--uu _f_u_n_c_t_i_o_n] [--rr _k_e_y_s_e_q] bbiinndd [--mm _k_e_y_m_a_p] --ff _f_i_l_e_n_a_m_e bbiinndd [--mm _k_e_y_m_a_p] --xx _k_e_y_s_e_q:_s_h_e_l_l_-_c_o_m_m_a_n_d bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_f_u_n_c_t_i_o_n_-_n_a_m_e bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d bbiinndd _r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d_-_l_i_n_e Display current rreeaaddlliinnee key and function bindings, bind a key sequence to a rreeaaddlliinnee function or macro, or set a rreeaaddlliinnee variable. Each non-option argument is a command as it would ap- pear in a rreeaaddlliinnee initialization file such as _._i_n_p_u_t_r_c, but each binding or command must be passed as a separate argument; e.g., '"\C-x\C-r": re-read-init-file'. Options, if supplied, have the following meanings: --mm _k_e_y_m_a_p Use _k_e_y_m_a_p as the keymap to be affected by the subsequent bindings. Acceptable _k_e_y_m_a_p names are _e_m_a_c_s_, _e_m_a_c_s_-_s_t_a_n_- _d_a_r_d_, _e_m_a_c_s_-_m_e_t_a_, _e_m_a_c_s_-_c_t_l_x_, _v_i_, _v_i_-_m_o_v_e_, _v_i_-_c_o_m_m_a_n_d, and _v_i_-_i_n_s_e_r_t. _v_i is equivalent to _v_i_-_c_o_m_m_a_n_d (_v_i_-_m_o_v_e is also a synonym); _e_m_a_c_s is equivalent to _e_m_a_c_s_-_s_t_a_n_- _d_a_r_d. --ll List the names of all rreeaaddlliinnee functions. --pp Display rreeaaddlliinnee function names and bindings in such a way that they can be re-read. --PP List current rreeaaddlliinnee function names and bindings. --ss Display rreeaaddlliinnee key sequences bound to macros and the strings they output in such a way that they can be re- read. --SS Display rreeaaddlliinnee key sequences bound to macros and the strings they output. --vv Display rreeaaddlliinnee variable names and values in such a way that they can be re-read. --VV List current rreeaaddlliinnee variable names and values. --ff _f_i_l_e_n_a_m_e Read key bindings from _f_i_l_e_n_a_m_e. --qq _f_u_n_c_t_i_o_n Query about which keys invoke the named _f_u_n_c_t_i_o_n. --uu _f_u_n_c_t_i_o_n Unbind all keys bound to the named _f_u_n_c_t_i_o_n. --rr _k_e_y_s_e_q Remove any current binding for _k_e_y_s_e_q. --xx _k_e_y_s_e_q::_s_h_e_l_l_-_c_o_m_m_a_n_d Cause _s_h_e_l_l_-_c_o_m_m_a_n_d to be executed whenever _k_e_y_s_e_q is en- tered. When _s_h_e_l_l_-_c_o_m_m_a_n_d is executed, the shell sets the RREEAADDLLIINNEE__LLIINNEE variable to the contents of the rreeaadd-- lliinnee line buffer and the RREEAADDLLIINNEE__PPOOIINNTT and RREEAADDLLIINNEE__MMAARRKK variables to the current location of the insertion point and the saved insertion point (the mark), respectively. The shell assigns any numeric argument the user supplied to the RREEAADDLLIINNEE__AARRGGUUMMEENNTT variable. If there was no argu- ment, that variable is not set. If the executed command changes the value of any of RREEAADDLLIINNEE__LLIINNEE, RREEAADD-- LLIINNEE__PPOOIINNTT, or RREEAADDLLIINNEE__MMAARRKK, those new values will be reflected in the editing state. --XX List all key sequences bound to shell commands and the associated commands in a format that can be reused as in- put. The return value is 0 unless an unrecognized option is given or an error occurred. bbrreeaakk [_n] Exit from within a ffoorr, wwhhiillee, uunnttiill, or sseelleecctt loop. If _n is specified, break _n levels. _n must be >= 1. If _n is greater than the number of enclosing loops, all enclosing loops are ex- ited. The return value is 0 unless _n is not greater than or equal to 1. bbuuiillttiinn _s_h_e_l_l_-_b_u_i_l_t_i_n [_a_r_g_u_m_e_n_t_s] Execute the specified shell builtin, passing it _a_r_g_u_m_e_n_t_s, and return its exit status. This is useful when defining a function whose name is the same as a shell builtin, retaining the func- tionality of the builtin within the function. The ccdd builtin is commonly redefined this way. The return status is false if _s_h_e_l_l_-_b_u_i_l_t_i_n is not a shell builtin command. ccaalllleerr [_e_x_p_r] Returns the context of any active subroutine call (a shell func- tion or a script executed with the .. or ssoouurrccee builtins). With- out _e_x_p_r, ccaalllleerr displays the line number and source filename of the current subroutine call. If a non-negative integer is sup- plied as _e_x_p_r, ccaalllleerr displays the line number, subroutine name, and source file corresponding to that position in the current execution call stack. This extra information may be used, for example, to print a stack trace. The current frame is frame 0. The return value is 0 unless the shell is not executing a sub- routine call or _e_x_p_r does not correspond to a valid position in the call stack. ccdd [--LL|[--PP [--ee]] [-@]] [_d_i_r] Change the current directory to _d_i_r. if _d_i_r is not supplied, the value of the HHOOMMEE shell variable is the default. The vari- able CCDDPPAATTHH defines the search path for the directory containing _d_i_r: each directory name in CCDDPPAATTHH is searched for _d_i_r. Alter- native directory names in CCDDPPAATTHH are separated by a colon (:). A null directory name in CCDDPPAATTHH is the same as the current di- rectory, i.e., ``..''. If _d_i_r begins with a slash (/), then CCDD-- PPAATTHH is not used. The --PP option causes ccdd to use the physical directory structure by resolving symbolic links while traversing _d_i_r and before processing instances of _._. in _d_i_r (see also the --PP option to the sseett builtin command); the --LL option forces sym- bolic links to be followed by resolving the link after process- ing instances of _._. in _d_i_r. If _._. appears in _d_i_r, it is pro- cessed by removing the immediately previous pathname component from _d_i_r, back to a slash or the beginning of _d_i_r. If the --ee option is supplied with --PP, and the current working directory cannot be successfully determined after a successful directory change, ccdd will return an unsuccessful status. On systems that support it, the --@@ option presents the extended attributes asso- ciated with a file as a directory. An argument of -- is con- verted to $$OOLLDDPPWWDD before the directory change is attempted. If a non-empty directory name from CCDDPPAATTHH is used, or if -- is the first argument, and the directory change is successful, the ab- solute pathname of the new working directory is written to the standard output. If the directory change is successful, ccdd sets the value of the PPWWDD environment variable to the new directory name, and sets the OOLLDDPPWWDD environment variable to the value of the current working directory before the change. The return value is true if the directory was successfully changed; false otherwise. ccoommmmaanndd [--ppVVvv] _c_o_m_m_a_n_d [_a_r_g ...] Run _c_o_m_m_a_n_d with _a_r_g_s suppressing the normal shell function lookup. Only builtin commands or commands found in the PPAATTHH are executed. If the --pp option is given, the search for _c_o_m_m_a_n_d is performed using a default value for PPAATTHH that is guaranteed to find all of the standard utilities. If either the --VV or --vv op- tion is supplied, a description of _c_o_m_m_a_n_d is printed. The --vv option causes a single word indicating the command or filename used to invoke _c_o_m_m_a_n_d to be displayed; the --VV option produces a more verbose description. If the --VV or --vv option is supplied, the exit status is 0 if _c_o_m_m_a_n_d was found, and 1 if not. If neither option is supplied and an error occurred or _c_o_m_m_a_n_d can- not be found, the exit status is 127. Otherwise, the exit sta- tus of the ccoommmmaanndd builtin is the exit status of _c_o_m_m_a_n_d. ccoommppggeenn [_o_p_t_i_o_n] [_w_o_r_d] Generate possible completion matches for _w_o_r_d according to the _o_p_t_i_o_ns, which may be any option accepted by the ccoommpplleettee builtin with the exception of --pp and --rr, and write the matches to the standard output. When using the --FF or --CC options, the various shell variables set by the programmable completion fa- cilities, while available, will not have useful values. The matches will be generated in the same way as if the program- mable completion code had generated them directly from a comple- tion specification with the same flags. If _w_o_r_d is specified, only those completions matching _w_o_r_d will be displayed. The return value is true unless an invalid option is supplied, or no matches were generated. ccoommpplleettee [--aabbccddeeffggjjkkssuuvv] [--oo _c_o_m_p_-_o_p_t_i_o_n] [--DDEEII] [--AA _a_c_t_i_o_n] [--GG _g_l_o_b_- _p_a_t] [--WW _w_o_r_d_l_i_s_t] [--FF _f_u_n_c_t_i_o_n] [--CC _c_o_m_m_a_n_d] [--XX _f_i_l_t_e_r_p_a_t] [--PP _p_r_e_f_i_x] [--SS _s_u_f_- _f_i_x] _n_a_m_e [_n_a_m_e _._._.] ccoommpplleettee --pprr [--DDEEII] [_n_a_m_e ...] Specify how arguments to each _n_a_m_e should be completed. If the --pp option is supplied, or if no options are supplied, existing completion specifications are printed in a way that allows them to be reused as input. The --rr option removes a completion spec- ification for each _n_a_m_e, or, if no _n_a_m_es are supplied, all com- pletion specifications. The --DD option indicates that other sup- plied options and actions should apply to the ``default'' com- mand completion; that is, completion attempted on a command for which no completion has previously been defined. The --EE option indicates that other supplied options and actions should apply to ``empty'' command completion; that is, completion attempted on a blank line. The --II option indicates that other supplied options and actions should apply to completion on the initial non-assignment word on the line, or after a command delimiter such as ;; or ||, which is usually command name completion. If multiple options are supplied, the --DD option takes precedence over --EE, and both take precedence over --II. If any of --DD, --EE, or --II are supplied, any other _n_a_m_e arguments are ignored; these completions only apply to the case specified by the option. The process of applying these completion specifications when word completion is attempted is described in _b_a_s_h_(_1_). Other options, if specified, have the following meanings. The arguments to the --GG, --WW, and --XX options (and, if necessary, the --PP and --SS options) should be quoted to protect them from expan- sion before the ccoommpplleettee builtin is invoked. --oo _c_o_m_p_-_o_p_t_i_o_n The _c_o_m_p_-_o_p_t_i_o_n controls several aspects of the comp- spec's behavior beyond the simple generation of comple- tions. _c_o_m_p_-_o_p_t_i_o_n may be one of: bbaasshhddeeffaauulltt Perform the rest of the default bbaasshh completions if the compspec generates no matches. ddeeffaauulltt Use readline's default filename completion if the compspec generates no matches. ddiirrnnaammeess Perform directory name completion if the comp- spec generates no matches. ffiilleennaammeess Tell readline that the compspec generates file- names, so it can perform any filename-specific processing (like adding a slash to directory names, quoting special characters, or suppress- ing trailing spaces). Intended to be used with shell functions. nnooqquuoottee Tell readline not to quote the completed words if they are filenames (quoting filenames is the default). nnoossoorrtt Tell readline not to sort the list of possible completions alphabetically. nnoossppaaccee Tell readline not to append a space (the de- fault) to words completed at the end of the line. pplluussddiirrss After any matches defined by the compspec are generated, directory name completion is at- tempted and any matches are added to the results of the other actions. --AA _a_c_t_i_o_n The _a_c_t_i_o_n may be one of the following to generate a list of possible completions: aalliiaass Alias names. May also be specified as --aa. aarrrraayyvvaarr Array variable names. bbiinnddiinngg RReeaaddlliinnee key binding names. bbuuiillttiinn Names of shell builtin commands. May also be specified as --bb. ccoommmmaanndd Command names. May also be specified as --cc. ddiirreeccttoorryy Directory names. May also be specified as --dd. ddiissaabblleedd Names of disabled shell builtins. eennaabblleedd Names of enabled shell builtins. eexxppoorrtt Names of exported shell variables. May also be specified as --ee. ffiillee File names. May also be specified as --ff. ffuunnccttiioonn Names of shell functions. ggrroouupp Group names. May also be specified as --gg. hheellppttooppiicc Help topics as accepted by the hheellpp builtin. hhoossttnnaammee Hostnames, as taken from the file specified by the HHOOSSTTFFIILLEE shell variable. jjoobb Job names, if job control is active. May also be specified as --jj. kkeeyywwoorrdd Shell reserved words. May also be specified as --kk. rruunnnniinngg Names of running jobs, if job control is active. sseerrvviiccee Service names. May also be specified as --ss. sseettoopptt Valid arguments for the --oo option to the sseett builtin. sshhoopptt Shell option names as accepted by the sshhoopptt builtin. ssiiggnnaall Signal names. ssttooppppeedd Names of stopped jobs, if job control is active. uusseerr User names. May also be specified as --uu. vvaarriiaabbllee Names of all shell variables. May also be spec- ified as --vv. --CC _c_o_m_m_a_n_d _c_o_m_m_a_n_d is executed in a subshell environment, and its output is used as the possible completions. Arguments are passed as with the --FF option. --FF _f_u_n_c_t_i_o_n The shell function _f_u_n_c_t_i_o_n is executed in the current shell environment. When the function is executed, the first argument ($$11) is the name of the command whose ar- guments are being completed, the second argument ($$22) is the word being completed, and the third argument ($$33) is the word preceding the word being completed on the cur- rent command line. When it finishes, the possible com- pletions are retrieved from the value of the CCOOMMPPRREEPPLLYY array variable. --GG _g_l_o_b_p_a_t The pathname expansion pattern _g_l_o_b_p_a_t is expanded to generate the possible completions. --PP _p_r_e_f_i_x _p_r_e_f_i_x is added at the beginning of each possible com- pletion after all other options have been applied. --SS _s_u_f_f_i_x _s_u_f_f_i_x is appended to each possible completion after all other options have been applied. --WW _w_o_r_d_l_i_s_t The _w_o_r_d_l_i_s_t is split using the characters in the IIFFSS special variable as delimiters, and each resultant word is expanded. Shell quoting is honored within _w_o_r_d_l_i_s_t, in order to provide a mechanism for the words to contain shell metacharacters or characters in the value of IIFFSS. The possible completions are the members of the resul- tant list which match the word being completed. --XX _f_i_l_t_e_r_p_a_t _f_i_l_t_e_r_p_a_t is a pattern as used for pathname expansion. It is applied to the list of possible completions gener- ated by the preceding options and arguments, and each completion matching _f_i_l_t_e_r_p_a_t is removed from the list. A leading !! in _f_i_l_t_e_r_p_a_t negates the pattern; in this case, any completion not matching _f_i_l_t_e_r_p_a_t is removed. The return value is true unless an invalid option is supplied, an option other than --pp or --rr is supplied without a _n_a_m_e argu- ment, an attempt is made to remove a completion specification for a _n_a_m_e for which no specification exists, or an error occurs adding a completion specification. ccoommppoopptt [--oo _o_p_t_i_o_n] [--DDEEII] [++oo _o_p_t_i_o_n] [_n_a_m_e] Modify completion options for each _n_a_m_e according to the _o_p_- _t_i_o_ns, or for the currently-executing completion if no _n_a_m_es are supplied. If no _o_p_t_i_o_ns are given, display the completion op- tions for each _n_a_m_e or the current completion. The possible values of _o_p_t_i_o_n are those valid for the ccoommpplleettee builtin de- scribed above. The --DD option indicates that other supplied op- tions should apply to the ``default'' command completion; that is, completion attempted on a command for which no completion has previously been defined. The --EE option indicates that other supplied options should apply to ``empty'' command completion; that is, completion attempted on a blank line. The --II option indicates that other supplied options should apply to completion on the initial non-assignment word on the line, or after a com- mand delimiter such as ;; or ||, which is usually command name completion. The return value is true unless an invalid option is supplied, an attempt is made to modify the options for a _n_a_m_e for which no completion specification exists, or an output error occurs. ccoonnttiinnuuee [_n] Resume the next iteration of the enclosing ffoorr, wwhhiillee, uunnttiill, or sseelleecctt loop. If _n is specified, resume at the _nth enclosing loop. _n must be >= 1. If _n is greater than the number of en- closing loops, the last enclosing loop (the ``top-level'' loop) is resumed. The return value is 0 unless _n is not greater than or equal to 1. ddeeccllaarree [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...] ttyyppeesseett [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...] Declare variables and/or give them attributes. If no _n_a_m_es are given then display the values of variables. The --pp option will display the attributes and values of each _n_a_m_e. When --pp is used with _n_a_m_e arguments, additional options, other than --ff and --FF, are ignored. When --pp is supplied without _n_a_m_e arguments, it will display the attributes and values of all variables having the attributes specified by the additional options. If no other options are supplied with --pp, ddeeccllaarree will display the at- tributes and values of all shell variables. The --ff option will restrict the display to shell functions. The --FF option inhibits the display of function definitions; only the function name and attributes are printed. If the eexxttddeebbuugg shell option is enabled using sshhoopptt, the source file name and line number where each _n_a_m_e is defined are displayed as well. The --FF option implies --ff. The --gg option forces variables to be created or modified at the global scope, even when ddeeccllaarree is executed in a shell func- tion. It is ignored in all other cases. The --II option causes local variables to inherit the attributes (except the _n_a_m_e_r_e_f attribute) and value of any existing variable with the same _n_a_m_e at a surrounding scope. If there is no existing variable, the local variable is initially unset. The following options can be used to restrict output to variables with the specified attri- bute or to give variables attributes: --aa Each _n_a_m_e is an indexed array variable (see AArrrraayyss in _b_a_s_h_(_1_)). --AA Each _n_a_m_e is an associative array variable (see AArrrraayyss in _b_a_s_h_(_1_)). --ff Use function names only. --ii The variable is treated as an integer; arithmetic evalua- tion (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN in _b_a_s_h_(_1_)) is performed when the variable is assigned a value. --ll When the variable is assigned a value, all upper-case characters are converted to lower-case. The upper-case attribute is disabled. --nn Give each _n_a_m_e the _n_a_m_e_r_e_f attribute, making it a name reference to another variable. That other variable is defined by the value of _n_a_m_e. All references, assign- ments, and attribute modifications to _n_a_m_e, except those using or changing the --nn attribute itself, are performed on the variable referenced by _n_a_m_e's value. The nameref attribute cannot be applied to array variables. --rr Make _n_a_m_es readonly. These names cannot then be assigned values by subsequent assignment statements or unset. --tt Give each _n_a_m_e the _t_r_a_c_e attribute. Traced functions in- herit the DDEEBBUUGG and RREETTUURRNN traps from the calling shell. The trace attribute has no special meaning for variables. --uu When the variable is assigned a value, all lower-case characters are converted to upper-case. The lower-case attribute is disabled. --xx Mark _n_a_m_es for export to subsequent commands via the en- vironment. Using `+' instead of `-' turns off the attribute instead, with the exceptions that ++aa and ++AA may not be used to destroy array variables and ++rr will not remove the readonly attribute. When used in a function, ddeeccllaarree and ttyyppeesseett make each _n_a_m_e local, as with the llooccaall command, unless the --gg option is supplied. If a variable name is followed by =_v_a_l_u_e, the value of the variable is set to _v_a_l_u_e. When using --aa or --AA and the compound assign- ment syntax to create array variables, additional attributes do not take effect until subsequent assignments. The return value is 0 unless an invalid option is encountered, an attempt is made to define a function using ``-f foo=bar'', an attempt is made to assign a value to a readonly variable, an attempt is made to as- sign a value to an array variable without using the compound as- signment syntax (see AArrrraayyss in _b_a_s_h_(_1_)), one of the _n_a_m_e_s is not a valid shell variable name, an attempt is made to turn off readonly status for a readonly variable, an attempt is made to turn off array status for an array variable, or an attempt is made to display a non-existent function with --ff. ddiirrss [[--ccllppvv]] [[++_n]] [[--_n]] Without options, displays the list of currently remembered di- rectories. The default display is on a single line with direc- tory names separated by spaces. Directories are added to the list with the ppuusshhdd command; the ppooppdd command removes entries from the list. The current directory is always the first direc- tory in the stack. --cc Clears the directory stack by deleting all of the en- tries. --ll Produces a listing using full pathnames; the default listing format uses a tilde to denote the home directory. --pp Print the directory stack with one entry per line. --vv Print the directory stack with one entry per line, pre- fixing each entry with its index in the stack. ++_n Displays the _nth entry counting from the left of the list shown by ddiirrss when invoked without options, starting with zero. --_n Displays the _nth entry counting from the right of the list shown by ddiirrss when invoked without options, starting with zero. The return value is 0 unless an invalid option is supplied or _n indexes beyond the end of the directory stack. ddiissoowwnn [--aarr] [--hh] [_j_o_b_s_p_e_c ... | _p_i_d ... ] Without options, remove each _j_o_b_s_p_e_c from the table of active jobs. If _j_o_b_s_p_e_c is not present, and neither the --aa nor the --rr option is supplied, the _c_u_r_r_e_n_t _j_o_b is used. If the --hh option is given, each _j_o_b_s_p_e_c is not removed from the table, but is marked so that SSIIGGHHUUPP is not sent to the job if the shell re- ceives a SSIIGGHHUUPP. If no _j_o_b_s_p_e_c is supplied, the --aa option means to remove or mark all jobs; the --rr option without a _j_o_b_s_p_e_c ar- gument restricts operation to running jobs. The return value is 0 unless a _j_o_b_s_p_e_c does not specify a valid job. eecchhoo [--nneeEE] [_a_r_g ...] Output the _a_r_gs, separated by spaces, followed by a newline. The return status is 0 unless a write error occurs. If --nn is specified, the trailing newline is suppressed. If the --ee option is given, interpretation of the following backslash-escaped characters is enabled. The --EE option disables the interpreta- tion of these escape characters, even on systems where they are interpreted by default. The xxppgg__eecchhoo shell option may be used to dynamically determine whether or not eecchhoo expands these es- cape characters by default. eecchhoo does not interpret ---- to mean the end of options. eecchhoo interprets the following escape se- quences: \\aa alert (bell) \\bb backspace \\cc suppress further output \\ee \\EE an escape character \\ff form feed \\nn new line \\rr carriage return \\tt horizontal tab \\vv vertical tab \\\\ backslash \\00_n_n_n the eight-bit character whose value is the octal value _n_n_n (zero to three octal digits) \\xx_H_H the eight-bit character whose value is the hexadecimal value _H_H (one or two hex digits) \\uu_H_H_H_H the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value _H_H_H_H (one to four hex digits) \\UU_H_H_H_H_H_H_H_H the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits) eennaabbllee [--aa] [--ddnnppss] [--ff _f_i_l_e_n_a_m_e] [_n_a_m_e ...] Enable and disable builtin shell commands. Disabling a builtin allows a disk command which has the same name as a shell builtin to be executed without specifying a full pathname, even though the shell normally searches for builtins before disk commands. If --nn is used, each _n_a_m_e is disabled; otherwise, _n_a_m_e_s are en- abled. For example, to use the tteesstt binary found via the PPAATTHH instead of the shell builtin version, run ``enable -n test''. The --ff option means to load the new builtin command _n_a_m_e from shared object _f_i_l_e_n_a_m_e, on systems that support dynamic loading. Bash will use the value of the BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH variable as a colon-separated list of directories in which to search for _f_i_l_e_- _n_a_m_e. The default is system-dependent. The --dd option will delete a builtin previously loaded with --ff. If no _n_a_m_e argu- ments are given, or if the --pp option is supplied, a list of shell builtins is printed. With no other option arguments, the list consists of all enabled shell builtins. If --nn is supplied, only disabled builtins are printed. If --aa is supplied, the list printed includes all builtins, with an indication of whether or not each is enabled. If --ss is supplied, the output is re- stricted to the POSIX _s_p_e_c_i_a_l builtins. If no options are sup- plied and a _n_a_m_e is not a shell builtin, eennaabbllee will attempt to load _n_a_m_e from a shared object named _n_a_m_e, as if the command were ``enable -f _n_a_m_e _n_a_m_e . The return value is 0 unless a _n_a_m_e is not a shell builtin or there is an error loading a new builtin from a shared object. eevvaall [_a_r_g ...] The _a_r_gs are read and concatenated together into a single com- mand. This command is then read and executed by the shell, and its exit status is returned as the value of eevvaall. If there are no _a_r_g_s, or only null arguments, eevvaall returns 0. eexxeecc [--ccll] [--aa _n_a_m_e] [_c_o_m_m_a_n_d [_a_r_g_u_m_e_n_t_s]] If _c_o_m_m_a_n_d is specified, it replaces the shell. No new process is created. The _a_r_g_u_m_e_n_t_s become the arguments to _c_o_m_m_a_n_d. If the --ll option is supplied, the shell places a dash at the begin- ning of the zeroth argument passed to _c_o_m_m_a_n_d. This is what _l_o_- _g_i_n(1) does. The --cc option causes _c_o_m_m_a_n_d to be executed with an empty environment. If --aa is supplied, the shell passes _n_a_m_e as the zeroth argument to the executed command. If _c_o_m_m_a_n_d can- not be executed for some reason, a non-interactive shell exits, unless the eexxeeccffaaiill shell option is enabled. In that case, it returns failure. An interactive shell returns failure if the file cannot be executed. A subshell exits unconditionally if eexxeecc fails. If _c_o_m_m_a_n_d is not specified, any redirections take effect in the current shell, and the return status is 0. If there is a redirection error, the return status is 1. eexxiitt [_n] Cause the shell to exit with a status of _n. If _n is omitted, the exit status is that of the last command executed. A trap on EEXXIITT is executed before the shell terminates. eexxppoorrtt [--ffnn] [_n_a_m_e[=_w_o_r_d]] ... eexxppoorrtt --pp The supplied _n_a_m_e_s are marked for automatic export to the envi- ronment of subsequently executed commands. If the --ff option is given, the _n_a_m_e_s refer to functions. If no _n_a_m_e_s are given, or if the --pp option is supplied, a list of names of all exported variables is printed. The --nn option causes the export property to be removed from each _n_a_m_e. If a variable name is followed by =_w_o_r_d, the value of the variable is set to _w_o_r_d. eexxppoorrtt returns an exit status of 0 unless an invalid option is encountered, one of the _n_a_m_e_s is not a valid shell variable name, or --ff is sup- plied with a _n_a_m_e that is not a function. ffcc [--ee _e_n_a_m_e] [--llnnrr] [_f_i_r_s_t] [_l_a_s_t] ffcc --ss [_p_a_t=_r_e_p] [_c_m_d] The first form selects a range of commands from _f_i_r_s_t to _l_a_s_t from the history list and displays or edits and re-executes them. _F_i_r_s_t and _l_a_s_t may be specified as a string (to locate the last command beginning with that string) or as a number (an index into the history list, where a negative number is used as an offset from the current command number). When listing, a _f_i_r_s_t or _l_a_s_t of 0 is equivalent to -1 and -0 is equivalent to the current command (usually the ffcc command); otherwise 0 is equivalent to -1 and -0 is invalid. If _l_a_s_t is not specified, it is set to the current command for listing (so that ``fc -l -10'' prints the last 10 commands) and to _f_i_r_s_t otherwise. If _f_i_r_s_t is not specified, it is set to the previous command for editing and -16 for listing. The --nn option suppresses the command numbers when listing. The --rr option reverses the order of the commands. If the --ll option is given, the commands are listed on standard output. Other- wise, the editor given by _e_n_a_m_e is invoked on a file containing those commands. If _e_n_a_m_e is not given, the value of the FFCCEEDDIITT variable is used, and the value of EEDDIITTOORR if FFCCEEDDIITT is not set. If neither variable is set, _v_i is used. When editing is com- plete, the edited commands are echoed and executed. In the second form, _c_o_m_m_a_n_d is re-executed after each instance of _p_a_t is replaced by _r_e_p. _C_o_m_m_a_n_d is interpreted the same as _f_i_r_s_t above. A useful alias to use with this is ``r="fc -s"'', so that typing ``r cc'' runs the last command beginning with ``cc'' and typing ``r'' re-executes the last command. If the first form is used, the return value is 0 unless an in- valid option is encountered or _f_i_r_s_t or _l_a_s_t specify history lines out of range. If the --ee option is supplied, the return value is the value of the last command executed or failure if an error occurs with the temporary file of commands. If the second form is used, the return status is that of the command re-exe- cuted, unless _c_m_d does not specify a valid history line, in which case ffcc returns failure. ffgg [_j_o_b_s_p_e_c] Resume _j_o_b_s_p_e_c in the foreground, and make it the current job. If _j_o_b_s_p_e_c is not present, the shell's notion of the _c_u_r_r_e_n_t _j_o_b is used. The return value is that of the command placed into the foreground, or failure if run when job control is disabled or, when run with job control enabled, if _j_o_b_s_p_e_c does not spec- ify a valid job or _j_o_b_s_p_e_c specifies a job that was started without job control. ggeettooppttss _o_p_t_s_t_r_i_n_g _n_a_m_e [_a_r_g _._._.] ggeettooppttss is used by shell procedures to parse positional parame- ters. _o_p_t_s_t_r_i_n_g contains the option characters to be recog- nized; if a character is followed by a colon, the option is ex- pected to have an argument, which should be separated from it by white space. The colon and question mark characters may not be used as option characters. Each time it is invoked, ggeettooppttss places the next option in the shell variable _n_a_m_e, initializing _n_a_m_e if it does not exist, and the index of the next argument to be processed into the variable OOPPTTIINNDD. OOPPTTIINNDD is initialized to 1 each time the shell or a shell script is invoked. When an op- tion requires an argument, ggeettooppttss places that argument into the variable OOPPTTAARRGG. The shell does not reset OOPPTTIINNDD automatically; it must be manually reset between multiple calls to ggeettooppttss within the same shell invocation if a new set of parameters is to be used. When the end of options is encountered, ggeettooppttss exits with a re- turn value greater than zero. OOPPTTIINNDD is set to the index of the first non-option argument, and _n_a_m_e is set to ?. ggeettooppttss normally parses the positional parameters, but if more arguments are supplied as _a_r_g values, ggeettooppttss parses those in- stead. ggeettooppttss can report errors in two ways. If the first character of _o_p_t_s_t_r_i_n_g is a colon, _s_i_l_e_n_t error reporting is used. In normal operation, diagnostic messages are printed when invalid options or missing option arguments are encountered. If the variable OOPPTTEERRRR is set to 0, no error messages will be dis- played, even if the first character of _o_p_t_s_t_r_i_n_g is not a colon. If an invalid option is seen, ggeettooppttss places ? into _n_a_m_e and, if not silent, prints an error message and unsets OOPPTTAARRGG. If ggeettooppttss is silent, the option character found is placed in OOPP-- TTAARRGG and no diagnostic message is printed. If a required argument is not found, and ggeettooppttss is not silent, a question mark (??) is placed in _n_a_m_e, OOPPTTAARRGG is unset, and a diagnostic message is printed. If ggeettooppttss is silent, then a colon (::) is placed in _n_a_m_e and OOPPTTAARRGG is set to the option character found. ggeettooppttss returns true if an option, specified or unspecified, is found. It returns false if the end of options is encountered or an error occurs. hhaasshh [--llrr] [--pp _f_i_l_e_n_a_m_e] [--ddtt] [_n_a_m_e] Each time hhaasshh is invoked, the full pathname of the command _n_a_m_e is determined by searching the directories in $$PPAATTHH and remem- bered. Any previously-remembered pathname is discarded. If the --pp option is supplied, no path search is performed, and _f_i_l_e_n_a_m_e is used as the full filename of the command. The --rr option causes the shell to forget all remembered locations. The --dd op- tion causes the shell to forget the remembered location of each _n_a_m_e. If the --tt option is supplied, the full pathname to which each _n_a_m_e corresponds is printed. If multiple _n_a_m_e arguments are supplied with --tt, the _n_a_m_e is printed before the hashed full pathname. The --ll option causes output to be displayed in a for- mat that may be reused as input. If no arguments are given, or if only --ll is supplied, information about remembered commands is printed. The return status is true unless a _n_a_m_e is not found or an invalid option is supplied. hheellpp [--ddmmss] [_p_a_t_t_e_r_n] Display helpful information about builtin commands. If _p_a_t_t_e_r_n is specified, hheellpp gives detailed help on all commands matching _p_a_t_t_e_r_n; otherwise help for all the builtins and shell control structures is printed. --dd Display a short description of each _p_a_t_t_e_r_n --mm Display the description of each _p_a_t_t_e_r_n in a manpage-like format --ss Display only a short usage synopsis for each _p_a_t_t_e_r_n The return status is 0 unless no command matches _p_a_t_t_e_r_n. hhiissttoorryy [[_n]] hhiissttoorryy --cc hhiissttoorryy --dd _o_f_f_s_e_t hhiissttoorryy --dd _s_t_a_r_t-_e_n_d hhiissttoorryy --aannrrww [_f_i_l_e_n_a_m_e] hhiissttoorryy --pp _a_r_g [_a_r_g _._._.] hhiissttoorryy --ss _a_r_g [_a_r_g _._._.] With no options, display the command history list with line num- bers. Lines listed with a ** have been modified. An argument of _n lists only the last _n lines. If the shell variable HHIISSTTTTIIMMEE-- FFOORRMMAATT is set and not null, it is used as a format string for _s_t_r_f_t_i_m_e(3) to display the time stamp associated with each dis- played history entry. No intervening blank is printed between the formatted time stamp and the history line. If _f_i_l_e_n_a_m_e is supplied, it is used as the name of the history file; if not, the value of HHIISSTTFFIILLEE is used. Options, if supplied, have the following meanings: --cc Clear the history list by deleting all the entries. --dd _o_f_f_s_e_t Delete the history entry at position _o_f_f_s_e_t. If _o_f_f_s_e_t is negative, it is interpreted as relative to one greater than the last history position, so negative indices count back from the end of the history, and an index of -1 refers to the current hhiissttoorryy --dd command. --dd _s_t_a_r_t-_e_n_d Delete the range of history entries between positions _s_t_a_r_t and _e_n_d, inclusive. Positive and negative values for _s_t_a_r_t and _e_n_d are interpreted as described above. --aa Append the ``new'' history lines to the history file. These are history lines entered since the beginning of the current bbaasshh session, but not already appended to the history file. --nn Read the history lines not already read from the history file into the current history list. These are lines ap- pended to the history file since the beginning of the current bbaasshh session. --rr Read the contents of the history file and append them to the current history list. --ww Write the current history list to the history file, over- writing the history file's contents. --pp Perform history substitution on the following _a_r_g_s and display the result on the standard output. Does not store the results in the history list. Each _a_r_g must be quoted to disable normal history expansion. --ss Store the _a_r_g_s in the history list as a single entry. The last command in the history list is removed before the _a_r_g_s are added. If the HHIISSTTTTIIMMEEFFOORRMMAATT variable is set, the time stamp informa- tion associated with each history entry is written to the his- tory file, marked with the history comment character. When the history file is read, lines beginning with the history comment character followed immediately by a digit are interpreted as timestamps for the following history entry. The return value is 0 unless an invalid option is encountered, an error occurs while reading or writing the history file, an invalid _o_f_f_s_e_t or range is supplied as an argument to --dd, or the history expansion sup- plied as an argument to --pp fails. jjoobbss [--llnnpprrss] [ _j_o_b_s_p_e_c ... ] jjoobbss --xx _c_o_m_m_a_n_d [ _a_r_g_s ... ] The first form lists the active jobs. The options have the fol- lowing meanings: --ll List process IDs in addition to the normal information. --nn Display information only about jobs that have changed status since the user was last notified of their status. --pp List only the process ID of the job's process group leader. --rr Display only running jobs. --ss Display only stopped jobs. If _j_o_b_s_p_e_c is given, output is restricted to information about that job. The return status is 0 unless an invalid option is encountered or an invalid _j_o_b_s_p_e_c is supplied. If the --xx option is supplied, jjoobbss replaces any _j_o_b_s_p_e_c found in _c_o_m_m_a_n_d or _a_r_g_s with the corresponding process group ID, and ex- ecutes _c_o_m_m_a_n_d passing it _a_r_g_s, returning its exit status. kkiillll [--ss _s_i_g_s_p_e_c | --nn _s_i_g_n_u_m | --_s_i_g_s_p_e_c] [_p_i_d | _j_o_b_s_p_e_c] ... kkiillll --ll|--LL [_s_i_g_s_p_e_c | _e_x_i_t___s_t_a_t_u_s] Send the signal named by _s_i_g_s_p_e_c or _s_i_g_n_u_m to the processes named by _p_i_d or _j_o_b_s_p_e_c. _s_i_g_s_p_e_c is either a case-insensitive signal name such as SSIIGGKKIILLLL (with or without the SSIIGG prefix) or a signal number; _s_i_g_n_u_m is a signal number. If _s_i_g_s_p_e_c is not present, then SSIIGGTTEERRMM is assumed. An argument of --ll lists the signal names. If any arguments are supplied when --ll is given, the names of the signals corresponding to the arguments are listed, and the return status is 0. The _e_x_i_t___s_t_a_t_u_s argument to --ll is a number specifying either a signal number or the exit status of a process terminated by a signal. The --LL option is equivalent to --ll. kkiillll returns true if at least one signal was successfully sent, or false if an error occurs or an invalid op- tion is encountered. lleett _a_r_g [_a_r_g ...] Each _a_r_g is an arithmetic expression to be evaluated (see AARRIITTHH-- MMEETTIICC EEVVAALLUUAATTIIOONN in _b_a_s_h_(_1_)). If the last _a_r_g evaluates to 0, lleett returns 1; 0 is returned otherwise. llooccaall [_o_p_t_i_o_n] [_n_a_m_e[=_v_a_l_u_e] ... | - ] For each argument, a local variable named _n_a_m_e is created, and assigned _v_a_l_u_e. The _o_p_t_i_o_n can be any of the options accepted by ddeeccllaarree. When llooccaall is used within a function, it causes the variable _n_a_m_e to have a visible scope restricted to that func- tion and its children. If _n_a_m_e is -, the set of shell options is made local to the function in which llooccaall is invoked: shell options changed using the sseett builtin inside the function are restored to their original values when the function returns. The restore is effected as if a series of sseett commands were exe- cuted to restore the values that were in place before the func- tion. With no operands, llooccaall writes a list of local variables to the standard output. It is an error to use llooccaall when not within a function. The return status is 0 unless llooccaall is used outside a function, an invalid _n_a_m_e is supplied, or _n_a_m_e is a readonly variable. llooggoouutt Exit a login shell. mmaappffiillee [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y] rreeaaddaarrrraayy [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y] Read lines from the standard input into the indexed array vari- able _a_r_r_a_y, or from file descriptor _f_d if the --uu option is sup- plied. The variable MMAAPPFFIILLEE is the default _a_r_r_a_y. Options, if supplied, have the following meanings: --dd The first character of _d_e_l_i_m is used to terminate each input line, rather than newline. If _d_e_l_i_m is the empty string, mmaappffiillee will terminate a line when it reads a NUL character. --nn Copy at most _c_o_u_n_t lines. If _c_o_u_n_t is 0, all lines are copied. --OO Begin assigning to _a_r_r_a_y at index _o_r_i_g_i_n. The default index is 0. --ss Discard the first _c_o_u_n_t lines read. --tt Remove a trailing _d_e_l_i_m (default newline) from each line read. --uu Read lines from file descriptor _f_d instead of the stan- dard input. --CC Evaluate _c_a_l_l_b_a_c_k each time _q_u_a_n_t_u_m lines are read. The --cc option specifies _q_u_a_n_t_u_m. --cc Specify the number of lines read between each call to _c_a_l_l_b_a_c_k. If --CC is specified without --cc, the default quantum is 5000. When _c_a_l_l_b_a_c_k is evaluated, it is supplied the index of the next array element to be assigned and the line to be assigned to that element as additional arguments. _c_a_l_l_b_a_c_k is evaluated after the line is read but before the array element is assigned. If not supplied with an explicit origin, mmaappffiillee will clear _a_r_- _r_a_y before assigning to it. mmaappffiillee returns successfully unless an invalid option or option argument is supplied, _a_r_r_a_y is invalid or unassignable, or if _a_r_r_a_y is not an indexed array. ppooppdd [-nn] [+_n] [-_n] Removes entries from the directory stack. The elements are num- bered from 0 starting at the first directory listed by ddiirrss. With no arguments, ppooppdd removes the top directory from the stack, and changes to the new top directory. Arguments, if sup- plied, have the following meanings: --nn Suppresses the normal change of directory when removing directories from the stack, so that only the stack is ma- nipulated. ++_n Removes the _nth entry counting from the left of the list shown by ddiirrss, starting with zero, from the stack. For example: ``popd +0'' removes the first directory, ``popd +1'' the second. --_n Removes the _nth entry counting from the right of the list shown by ddiirrss, starting with zero. For example: ``popd -0'' removes the last directory, ``popd -1'' the next to last. If the top element of the directory stack is modified, and the _-_n option was not supplied, ppooppdd uses the ccdd builtin to change to the directory at the top of the stack. If the ccdd fails, ppooppdd returns a non-zero value. Otherwise, ppooppdd returns false if an invalid option is encoun- tered, the directory stack is empty, or a non-existent directory stack entry is specified. If the ppooppdd command is successful, bash runs ddiirrss to show the final contents of the directory stack, and the return status is 0. pprriinnttff [--vv _v_a_r] _f_o_r_m_a_t [_a_r_g_u_m_e_n_t_s] Write the formatted _a_r_g_u_m_e_n_t_s to the standard output under the control of the _f_o_r_m_a_t. The --vv option causes the output to be assigned to the variable _v_a_r rather than being printed to the standard output. The _f_o_r_m_a_t is a character string which contains three types of objects: plain characters, which are simply copied to standard output, character escape sequences, which are converted and copied to the standard output, and format specifications, each of which causes printing of the next successive _a_r_g_u_m_e_n_t. In addition to the standard _p_r_i_n_t_f(1) format specifications, pprriinnttff interprets the following extensions: %%bb causes pprriinnttff to expand backslash escape sequences in the corresponding _a_r_g_u_m_e_n_t in the same way as eecchhoo --ee. %%qq causes pprriinnttff to output the corresponding _a_r_g_u_m_e_n_t in a format that can be reused as shell input. %%QQ like %%qq, but applies any supplied precision to the _a_r_g_u_- _m_e_n_t before quoting it. %%((_d_a_t_e_f_m_t))TT causes pprriinnttff to output the date-time string resulting from using _d_a_t_e_f_m_t as a format string for _s_t_r_f_t_i_m_e(3). The corresponding _a_r_g_u_m_e_n_t is an integer representing the number of seconds since the epoch. Two special argument values may be used: -1 represents the current time, and -2 represents the time the shell was invoked. If no ar- gument is specified, conversion behaves as if -1 had been given. This is an exception to the usual pprriinnttff behav- ior. The %b, %q, and %T directives all use the field width and preci- sion arguments from the format specification and write that many bytes from (or use that wide a field for) the expanded argument, which usually contains more characters than the original. Arguments to non-string format specifiers are treated as C con- stants, except that a leading plus or minus sign is allowed, and if the leading character is a single or double quote, the value is the ASCII value of the following character. The _f_o_r_m_a_t is reused as necessary to consume all of the _a_r_g_u_- _m_e_n_t_s. If the _f_o_r_m_a_t requires more _a_r_g_u_m_e_n_t_s than are supplied, the extra format specifications behave as if a zero value or null string, as appropriate, had been supplied. The return value is zero on success, non-zero on failure. ppuusshhdd [--nn] [+_n] [-_n] ppuusshhdd [--nn] [_d_i_r] Adds a directory to the top of the directory stack, or rotates the stack, making the new top of the stack the current working directory. With no arguments, ppuusshhdd exchanges the top two ele- ments of the directory stack. Arguments, if supplied, have the following meanings: --nn Suppresses the normal change of directory when rotating or adding directories to the stack, so that only the stack is manipulated. ++_n Rotates the stack so that the _nth directory (counting from the left of the list shown by ddiirrss, starting with zero) is at the top. --_n Rotates the stack so that the _nth directory (counting from the right of the list shown by ddiirrss, starting with zero) is at the top. _d_i_r Adds _d_i_r to the directory stack at the top After the stack has been modified, if the --nn option was not sup- plied, ppuusshhdd uses the ccdd builtin to change to the directory at the top of the stack. If the ccdd fails, ppuusshhdd returns a non-zero value. Otherwise, if no arguments are supplied, ppuusshhdd returns 0 unless the directory stack is empty. When rotating the directory stack, ppuusshhdd returns 0 unless the directory stack is empty or a non-existent directory stack element is specified. If the ppuusshhdd command is successful, bash runs ddiirrss to show the final contents of the directory stack. ppwwdd [--LLPP] Print the absolute pathname of the current working directory. The pathname printed contains no symbolic links if the --PP option is supplied or the --oo pphhyyssiiccaall option to the sseett builtin command is enabled. If the --LL option is used, the pathname printed may contain symbolic links. The return status is 0 unless an error occurs while reading the name of the current directory or an in- valid option is supplied. rreeaadd [--eerrss] [--aa _a_n_a_m_e] [--dd _d_e_l_i_m] [--ii _t_e_x_t] [--nn _n_c_h_a_r_s] [--NN _n_c_h_a_r_s] [--pp _p_r_o_m_p_t] [--tt _t_i_m_e_o_u_t] [--uu _f_d] [_n_a_m_e ...] One line is read from the standard input, or from the file de- scriptor _f_d supplied as an argument to the --uu option, split into words as described in _b_a_s_h_(_1_) under WWoorrdd SSpplliittttiinngg, and the first word is assigned to the first _n_a_m_e, the second word to the second _n_a_m_e, and so on. If there are more words than names, the remaining words and their intervening delimiters are assigned to the last _n_a_m_e. If there are fewer words read from the input stream than names, the remaining names are assigned empty val- ues. The characters in IIFFSS are used to split the line into words using the same rules the shell uses for expansion (de- scribed in _b_a_s_h_(_1_) under WWoorrdd SSpplliittttiinngg). The backslash charac- ter (\\) may be used to remove any special meaning for the next character read and for line continuation. Options, if supplied, have the following meanings: --aa _a_n_a_m_e The words are assigned to sequential indices of the array variable _a_n_a_m_e, starting at 0. _a_n_a_m_e is unset before any new values are assigned. Other _n_a_m_e arguments are ig- nored. --dd _d_e_l_i_m The first character of _d_e_l_i_m is used to terminate the in- put line, rather than newline. If _d_e_l_i_m is the empty string, rreeaadd will terminate a line when it reads a NUL character. --ee If the standard input is coming from a terminal, rreeaaddlliinnee (see RREEAADDLLIINNEE in _b_a_s_h_(_1_)) is used to obtain the line. Readline uses the current (or default, if line editing was not previously active) editing settings, but uses readline's default filename completion. --ii _t_e_x_t If rreeaaddlliinnee is being used to read the line, _t_e_x_t is placed into the editing buffer before editing begins. --nn _n_c_h_a_r_s rreeaadd returns after reading _n_c_h_a_r_s characters rather than waiting for a complete line of input, but honors a delim- iter if fewer than _n_c_h_a_r_s characters are read before the delimiter. --NN _n_c_h_a_r_s rreeaadd returns after reading exactly _n_c_h_a_r_s characters rather than waiting for a complete line of input, unless EOF is encountered or rreeaadd times out. Delimiter charac- ters encountered in the input are not treated specially and do not cause rreeaadd to return until _n_c_h_a_r_s characters are read. The result is not split on the characters in IIFFSS; the intent is that the variable is assigned exactly the characters read (with the exception of backslash; see the --rr option below). --pp _p_r_o_m_p_t Display _p_r_o_m_p_t on standard error, without a trailing new- line, before attempting to read any input. The prompt is displayed only if input is coming from a terminal. --rr Backslash does not act as an escape character. The back- slash is considered to be part of the line. In particu- lar, a backslash-newline pair may not then be used as a line continuation. --ss Silent mode. If input is coming from a terminal, charac- ters are not echoed. --tt _t_i_m_e_o_u_t Cause rreeaadd to time out and return failure if a complete line of input (or a specified number of characters) is not read within _t_i_m_e_o_u_t seconds. _t_i_m_e_o_u_t may be a deci- mal number with a fractional portion following the deci- mal point. This option is only effective if rreeaadd is reading input from a terminal, pipe, or other special file; it has no effect when reading from regular files. If rreeaadd times out, rreeaadd saves any partial input read into the specified variable _n_a_m_e. If _t_i_m_e_o_u_t is 0, rreeaadd re- turns immediately, without trying to read any data. The exit status is 0 if input is available on the specified file descriptor, or the read will return EOF, non-zero otherwise. The exit status is greater than 128 if the timeout is exceeded. --uu _f_d Read input from file descriptor _f_d. If no _n_a_m_e_s are supplied, the line read, without the ending de- limiter but otherwise unmodified, is assigned to the variable RREEPPLLYY. The exit status is zero, unless end-of-file is encoun- tered, rreeaadd times out (in which case the status is greater than 128), a variable assignment error (such as assigning to a read- only variable) occurs, or an invalid file descriptor is supplied as the argument to --uu. rreeaaddoonnllyy [--aaAAff] [--pp] [_n_a_m_e[=_w_o_r_d] ...] The given _n_a_m_e_s are marked readonly; the values of these _n_a_m_e_s may not be changed by subsequent assignment. If the --ff option is supplied, the functions corresponding to the _n_a_m_e_s are so marked. The --aa option restricts the variables to indexed ar- rays; the --AA option restricts the variables to associative ar- rays. If both options are supplied, --AA takes precedence. If no _n_a_m_e arguments are given, or if the --pp option is supplied, a list of all readonly names is printed. The other options may be used to restrict the output to a subset of the set of readonly names. The --pp option causes output to be displayed in a format that may be reused as input. If a variable name is followed by =_w_o_r_d, the value of the variable is set to _w_o_r_d. The return status is 0 unless an invalid option is encountered, one of the _n_a_m_e_s is not a valid shell variable name, or --ff is supplied with a _n_a_m_e that is not a function. rreettuurrnn [_n] Causes a function to stop executing and return the value speci- fied by _n to its caller. If _n is omitted, the return status is that of the last command executed in the function body. If rree-- ttuurrnn is executed by a trap handler, the last command used to de- termine the status is the last command executed before the trap handler. If rreettuurrnn is executed during a DDEEBBUUGG trap, the last command used to determine the status is the last command exe- cuted by the trap handler before rreettuurrnn was invoked. If rreettuurrnn is used outside a function, but during execution of a script by the .. (ssoouurrccee) command, it causes the shell to stop executing that script and return either _n or the exit status of the last command executed within the script as the exit status of the script. If _n is supplied, the return value is its least signif- icant 8 bits. The return status is non-zero if rreettuurrnn is sup- plied a non-numeric argument, or is used outside a function and not during execution of a script by .. or ssoouurrccee. Any command associated with the RREETTUURRNN trap is executed before execution re- sumes after the function or script. sseett [--aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [--oo _o_p_t_i_o_n_-_n_a_m_e] [----] [--] [_a_r_g ...] sseett [++aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [++oo _o_p_t_i_o_n_-_n_a_m_e] [----] [--] [_a_r_g ...] Without options, display the name and value of each shell vari- able in a format that can be reused as input for setting or re- setting the currently-set variables. Read-only variables cannot be reset. In _p_o_s_i_x _m_o_d_e, only shell variables are listed. The output is sorted according to the current locale. When options are specified, they set or unset shell attributes. Any argu- ments remaining after option processing are treated as values for the positional parameters and are assigned, in order, to $$11, $$22, ...... $$_n. Options, if specified, have the following mean- ings: --aa Each variable or function that is created or modified is given the export attribute and marked for export to the environment of subsequent commands. --bb Report the status of terminated background jobs immedi- ately, rather than before the next primary prompt. This is effective only when job control is enabled. --ee Exit immediately if a _p_i_p_e_l_i_n_e (which may consist of a single _s_i_m_p_l_e _c_o_m_m_a_n_d), a _l_i_s_t, or a _c_o_m_p_o_u_n_d _c_o_m_m_a_n_d (see SSHHEELLLL GGRRAAMMMMAARR in _b_a_s_h_(_1_)), exits with a non-zero status. The shell does not exit if the command that fails is part of the command list immediately following a wwhhiillee or uunnttiill keyword, part of the test following the iiff or eelliiff reserved words, part of any command executed in a &&&& or |||| list except the command following the fi- nal &&&& or ||||, any command in a pipeline but the last, or if the command's return value is being inverted with !!. If a compound command other than a subshell returns a non-zero status because a command failed while --ee was being ignored, the shell does not exit. A trap on EERRRR, if set, is executed before the shell exits. This option applies to the shell environment and each subshell envi- ronment separately (see CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT in _b_a_s_h_(_1_)), and may cause subshells to exit before execut- ing all the commands in the subshell. If a compound command or shell function executes in a context where --ee is being ignored, none of the commands executed within the compound command or function body will be affected by the --ee setting, even if --ee is set and a command returns a failure status. If a compound command or shell function sets --ee while executing in a context where --ee is ignored, that setting will not have any effect until the compound command or the command containing the function call completes. --ff Disable pathname expansion. --hh Remember the location of commands as they are looked up for execution. This is enabled by default. --kk All arguments in the form of assignment statements are placed in the environment for a command, not just those that precede the command name. --mm Monitor mode. Job control is enabled. This option is on by default for interactive shells on systems that support it (see JJOOBB CCOONNTTRROOLL in _b_a_s_h_(_1_)). All processes run in a separate process group. When a background job completes, the shell prints a line containing its exit status. --nn Read commands but do not execute them. This may be used to check a shell script for syntax errors. This is ig- nored by interactive shells. --oo _o_p_t_i_o_n_-_n_a_m_e The _o_p_t_i_o_n_-_n_a_m_e can be one of the following: aalllleexxppoorrtt Same as --aa. bbrraacceeeexxppaanndd Same as --BB. eemmaaccss Use an emacs-style command line editing inter- face. This is enabled by default when the shell is interactive, unless the shell is started with the ----nnooeeddiittiinngg option. This also affects the editing interface used for rreeaadd --ee. eerrrreexxiitt Same as --ee. eerrrrttrraaccee Same as --EE. ffuunnccttrraaccee Same as --TT. hhaasshhaallll Same as --hh. hhiisstteexxppaanndd Same as --HH. hhiissttoorryy Enable command history, as described in _b_a_s_h_(_1_) under HHIISSTTOORRYY. This option is on by default in interactive shells. iiggnnoorreeeeooff The effect is as if the shell command ``IG- NOREEOF=10'' had been executed (see SShheellll VVaarrii-- aabblleess in _b_a_s_h_(_1_)). kkeeyywwoorrdd Same as --kk. mmoonniittoorr Same as --mm. nnoocclloobbbbeerr Same as --CC. nnooeexxeecc Same as --nn. nnoogglloobb Same as --ff. nnoolloogg Currently ignored. nnoottiiffyy Same as --bb. nnoouunnsseett Same as --uu. oonneeccmmdd Same as --tt. pphhyyssiiccaall Same as --PP. ppiippeeffaaiill If set, the return value of a pipeline is the value of the last (rightmost) command to exit with a non-zero status, or zero if all commands in the pipeline exit successfully. This option is disabled by default. ppoossiixx Change the behavior of bbaasshh where the default operation differs from the POSIX standard to match the standard (_p_o_s_i_x _m_o_d_e). See SSEEEE AALLSSOO in _b_a_s_h_(_1_) for a reference to a document that details how posix mode affects bash's behavior. pprriivviilleeggeedd Same as --pp. vveerrbboossee Same as --vv. vvii Use a vi-style command line editing interface. This also affects the editing interface used for rreeaadd --ee. xxttrraaccee Same as --xx. If --oo is supplied with no _o_p_t_i_o_n_-_n_a_m_e, the values of the current options are printed. If ++oo is supplied with no _o_p_t_i_o_n_-_n_a_m_e, a series of sseett commands to recreate the current option settings is displayed on the standard output. --pp Turn on _p_r_i_v_i_l_e_g_e_d mode. In this mode, the $$EENNVV and $$BBAASSHH__EENNVV files are not processed, shell functions are not inherited from the environment, and the SSHHEELLLLOOPPTTSS, BBAASSHHOOPPTTSS, CCDDPPAATTHH, and GGLLOOBBIIGGNNOORREE variables, if they ap- pear in the environment, are ignored. If the shell is started with the effective user (group) id not equal to the real user (group) id, and the --pp option is not sup- plied, these actions are taken and the effective user id is set to the real user id. If the --pp option is sup- plied at startup, the effective user id is not reset. Turning this option off causes the effective user and group ids to be set to the real user and group ids. --rr Enable restricted shell mode. This option cannot be un- set once it has been set. --tt Exit after reading and executing one command. --uu Treat unset variables and parameters other than the spe- cial parameters "@" and "*", or array variables sub- scripted with "@" or "*", as an error when performing parameter expansion. If expansion is attempted on an unset variable or parameter, the shell prints an error message, and, if not interactive, exits with a non-zero status. --vv Print shell input lines as they are read. --xx After expanding each _s_i_m_p_l_e _c_o_m_m_a_n_d, ffoorr command, ccaassee command, sseelleecctt command, or arithmetic ffoorr command, dis- play the expanded value of PPSS44, followed by the command and its expanded arguments or associated word list. --BB The shell performs brace expansion (see BBrraaccee EExxppaannssiioonn in _b_a_s_h_(_1_)). This is on by default. --CC If set, bbaasshh does not overwrite an existing file with the >>, >>&&, and <<>> redirection operators. This may be overridden when creating output files by using the redi- rection operator >>|| instead of >>. --EE If set, any trap on EERRRR is inherited by shell functions, command substitutions, and commands executed in a sub- shell environment. The EERRRR trap is normally not inher- ited in such cases. --HH Enable !! style history substitution. This option is on by default when the shell is interactive. --PP If set, the shell does not resolve symbolic links when executing commands such as ccdd that change the current working directory. It uses the physical directory structure instead. By default, bbaasshh follows the logical chain of directories when performing commands which change the current directory. --TT If set, any traps on DDEEBBUUGG and RREETTUURRNN are inherited by shell functions, command substitutions, and commands ex- ecuted in a subshell environment. The DDEEBBUUGG and RREETTUURRNN traps are normally not inherited in such cases. ---- If no arguments follow this option, then the positional parameters are unset. Otherwise, the positional parame- ters are set to the _a_r_gs, even if some of them begin with a --. -- Signal the end of options, cause all remaining _a_r_gs to be assigned to the positional parameters. The --xx and --vv options are turned off. If there are no _a_r_gs, the posi- tional parameters remain unchanged. The options are off by default unless otherwise noted. Using + rather than - causes these options to be turned off. The op- tions can also be specified as arguments to an invocation of the shell. The current set of options may be found in $$--. The re- turn status is always true unless an invalid option is encoun- tered. sshhiifftt [_n] The positional parameters from _n+1 ... are renamed to $$11 ........ Parameters represented by the numbers $$## down to $$##-_n+1 are un- set. _n must be a non-negative number less than or equal to $$##. If _n is 0, no parameters are changed. If _n is not given, it is assumed to be 1. If _n is greater than $$##, the positional param- eters are not changed. The return status is greater than zero if _n is greater than $$## or less than zero; otherwise 0. sshhoopptt [--ppqqssuu] [--oo] [_o_p_t_n_a_m_e ...] Toggle the values of settings controlling optional shell behav- ior. The settings can be either those listed below, or, if the --oo option is used, those available with the --oo option to the sseett builtin command. With no options, or with the --pp option, a list of all settable options is displayed, with an indication of whether or not each is set; if _o_p_t_n_a_m_e_s are supplied, the output is restricted to those options. The --pp option causes output to be displayed in a form that may be reused as input. Other op- tions have the following meanings: --ss Enable (set) each _o_p_t_n_a_m_e. --uu Disable (unset) each _o_p_t_n_a_m_e. --qq Suppresses normal output (quiet mode); the return status indicates whether the _o_p_t_n_a_m_e is set or unset. If multi- ple _o_p_t_n_a_m_e arguments are given with --qq, the return sta- tus is zero if all _o_p_t_n_a_m_e_s are enabled; non-zero other- wise. --oo Restricts the values of _o_p_t_n_a_m_e to be those defined for the --oo option to the sseett builtin. If either --ss or --uu is used with no _o_p_t_n_a_m_e arguments, sshhoopptt shows only those options which are set or unset, respectively. Unless otherwise noted, the sshhoopptt options are disabled (unset) by default. The return status when listing options is zero if all _o_p_t_n_a_m_e_s are enabled, non-zero otherwise. When setting or unsetting op- tions, the return status is zero unless an _o_p_t_n_a_m_e is not a valid shell option. The list of sshhoopptt options is: aassssoocc__eexxppaanndd__oonnccee If set, the shell suppresses multiple evaluation of as- sociative array subscripts during arithmetic expression evaluation, while executing builtins that can perform variable assignments, and while executing builtins that perform array dereferencing. aauuttooccdd If set, a command name that is the name of a directory is executed as if it were the argument to the ccdd com- mand. This option is only used by interactive shells. ccddaabbllee__vvaarrss If set, an argument to the ccdd builtin command that is not a directory is assumed to be the name of a variable whose value is the directory to change to. ccddssppeellll If set, minor errors in the spelling of a directory com- ponent in a ccdd command will be corrected. The errors checked for are transposed characters, a missing charac- ter, and one character too many. If a correction is found, the corrected filename is printed, and the com- mand proceeds. This option is only used by interactive shells. cchheecckkhhaasshh If set, bbaasshh checks that a command found in the hash ta- ble exists before trying to execute it. If a hashed command no longer exists, a normal path search is per- formed. cchheecckkjjoobbss If set, bbaasshh lists the status of any stopped and running jobs before exiting an interactive shell. If any jobs are running, this causes the exit to be deferred until a second exit is attempted without an intervening command (see JJOOBB CCOONNTTRROOLL in _b_a_s_h_(_1_)). The shell always post- pones exiting if any jobs are stopped. cchheecckkwwiinnssiizzee If set, bbaasshh checks the window size after each external (non-builtin) command and, if necessary, updates the values of LLIINNEESS and CCOOLLUUMMNNSS. This option is enabled by default. ccmmddhhiisstt If set, bbaasshh attempts to save all lines of a multiple- line command in the same history entry. This allows easy re-editing of multi-line commands. This option is enabled by default, but only has an effect if command history is enabled, as described in _b_a_s_h_(_1_) under HHIISS-- TTOORRYY. ccoommppaatt3311 ccoommppaatt3322 ccoommppaatt4400 ccoommppaatt4411 ccoommppaatt4422 ccoommppaatt4433 ccoommppaatt4444 ccoommppaatt5500 These control aspects of the shell's compatibility mode (see SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE in _b_a_s_h_(_1_)). ccoommpplleettee__ffuullllqquuoottee If set, bbaasshh quotes all shell metacharacters in file- names and directory names when performing completion. If not set, bbaasshh removes metacharacters such as the dol- lar sign from the set of characters that will be quoted in completed filenames when these metacharacters appear in shell variable references in words to be completed. This means that dollar signs in variable names that ex- pand to directories will not be quoted; however, any dollar signs appearing in filenames will not be quoted, either. This is active only when bash is using back- slashes to quote completed filenames. This variable is set by default, which is the default bash behavior in versions through 4.2. ddiirreexxppaanndd If set, bbaasshh replaces directory names with the results of word expansion when performing filename completion. This changes the contents of the readline editing buf- fer. If not set, bbaasshh attempts to preserve what the user typed. ddiirrssppeellll If set, bbaasshh attempts spelling correction on directory names during word completion if the directory name ini- tially supplied does not exist. ddoottgglloobb If set, bbaasshh includes filenames beginning with a `.' in the results of pathname expansion. The filenames ````..'''' and ````....'''' must always be matched explicitly, even if ddoottgglloobb is set. eexxeeccffaaiill If set, a non-interactive shell will not exit if it can- not execute the file specified as an argument to the eexxeecc builtin command. An interactive shell does not exit if eexxeecc fails. eexxppaanndd__aalliiaasseess If set, aliases are expanded as described in _b_a_s_h_(_1_) un- der AALLIIAASSEESS. This option is enabled by default for in- teractive shells. eexxttddeebbuugg If set at shell invocation, or in a shell startup file, arrange to execute the debugger profile before the shell starts, identical to the ----ddeebbuuggggeerr option. If set af- ter invocation, behavior intended for use by debuggers is enabled: 11.. The --FF option to the ddeeccllaarree builtin displays the source file name and line number corresponding to each function name supplied as an argument. 22.. If the command run by the DDEEBBUUGG trap returns a non-zero value, the next command is skipped and not executed. 33.. If the command run by the DDEEBBUUGG trap returns a value of 2, and the shell is executing in a sub- routine (a shell function or a shell script exe- cuted by the .. or ssoouurrccee builtins), the shell simulates a call to rreettuurrnn. 44.. BBAASSHH__AARRGGCC and BBAASSHH__AARRGGVV are updated as described in their descriptions in _b_a_s_h_(_1_)). 55.. Function tracing is enabled: command substitu- tion, shell functions, and subshells invoked with (( _c_o_m_m_a_n_d )) inherit the DDEEBBUUGG and RREETTUURRNN traps. 66.. Error tracing is enabled: command substitution, shell functions, and subshells invoked with (( _c_o_m_m_a_n_d )) inherit the EERRRR trap. eexxttgglloobb If set, the extended pattern matching features described in _b_a_s_h_(_1_) under PPaatthhnnaammee EExxppaannssiioonn are enabled. eexxttqquuoottee If set, $$'_s_t_r_i_n_g' and $$"_s_t_r_i_n_g" quoting is performed within $${{_p_a_r_a_m_e_t_e_r}} expansions enclosed in double quotes. This option is enabled by default. ffaaiillgglloobb If set, patterns which fail to match filenames during pathname expansion result in an expansion error. ffoorrccee__ffiiggnnoorree If set, the suffixes specified by the FFIIGGNNOORREE shell variable cause words to be ignored when performing word completion even if the ignored words are the only possi- ble completions. See SSHHEELLLL VVAARRIIAABBLLEESS in _b_a_s_h_(_1_) for a description of FFIIGGNNOORREE. This option is enabled by de- fault. gglloobbaasscciiiirraannggeess If set, range expressions used in pattern matching bracket expressions (see PPaatttteerrnn MMaattcchhiinngg in _b_a_s_h_(_1_)) behave as if in the traditional C locale when performing comparisons. That is, the current locale's collating sequence is not taken into account, so bb will not col- late between AA and BB, and upper-case and lower-case ASCII characters will collate together. gglloobbsskkiippddoottss If set, pathname expansion will never match the file- names ````..'''' and ````....'''', even if the pattern begins with a ````..''''. This option is enabled by default. gglloobbssttaarr If set, the pattern **** used in a pathname expansion con- text will match all files and zero or more directories and subdirectories. If the pattern is followed by a //, only directories and subdirectories match. ggnnuu__eerrrrffmmtt If set, shell error messages are written in the standard GNU error message format. hhiissttaappppeenndd If set, the history list is appended to the file named by the value of the HHIISSTTFFIILLEE variable when the shell ex- its, rather than overwriting the file. hhiissttrreeeeddiitt If set, and rreeaaddlliinnee is being used, a user is given the opportunity to re-edit a failed history substitution. hhiissttvveerriiffyy If set, and rreeaaddlliinnee is being used, the results of his- tory substitution are not immediately passed to the shell parser. Instead, the resulting line is loaded into the rreeaaddlliinnee editing buffer, allowing further modi- fication. hhoossttccoommpplleettee If set, and rreeaaddlliinnee is being used, bbaasshh will attempt to perform hostname completion when a word containing a @@ is being completed (see CCoommpplleettiinngg under RREEAADDLLIINNEE in _b_a_s_h_(_1_)). This is enabled by default. hhuuppoonneexxiitt If set, bbaasshh will send SSIIGGHHUUPP to all jobs when an inter- active login shell exits. iinnhheerriitt__eerrrreexxiitt If set, command substitution inherits the value of the eerrrreexxiitt option, instead of unsetting it in the subshell environment. This option is enabled when _p_o_s_i_x _m_o_d_e is enabled. iinntteerraaccttiivvee__ccoommmmeennttss If set, allow a word beginning with ## to cause that word and all remaining characters on that line to be ignored in an interactive shell (see CCOOMMMMEENNTTSS in _b_a_s_h_(_1_)). This option is enabled by default. llaassttppiippee If set, and job control is not active, the shell runs the last command of a pipeline not executed in the back- ground in the current shell environment. lliitthhiisstt If set, and the ccmmddhhiisstt option is enabled, multi-line commands are saved to the history with embedded newlines rather than using semicolon separators where possible. llooccaallvvaarr__iinnhheerriitt If set, local variables inherit the value and attributes of a variable of the same name that exists at a previous scope before any new value is assigned. The nameref at- tribute is not inherited. llooccaallvvaarr__uunnsseett If set, calling uunnsseett on local variables in previous function scopes marks them so subsequent lookups find them unset until that function returns. This is identi- cal to the behavior of unsetting local variables at the current function scope. llooggiinn__sshheellll The shell sets this option if it is started as a login shell (see IINNVVOOCCAATTIIOONN in _b_a_s_h_(_1_)). The value may not be changed. mmaaiillwwaarrnn If set, and a file that bbaasshh is checking for mail has been accessed since the last time it was checked, the message ``The mail in _m_a_i_l_f_i_l_e has been read'' is dis- played. nnoo__eemmppttyy__ccmmdd__ccoommpplleettiioonn If set, and rreeaaddlliinnee is being used, bbaasshh will not at- tempt to search the PPAATTHH for possible completions when completion is attempted on an empty line. nnooccaasseegglloobb If set, bbaasshh matches filenames in a case-insensitive fashion when performing pathname expansion (see PPaatthhnnaammee EExxppaannssiioonn in _b_a_s_h_(_1_)). nnooccaasseemmaattcchh If set, bbaasshh matches patterns in a case-insensitive fashion when performing matching while executing ccaassee or [[[[ conditional commands, when performing pattern substi- tution word expansions, or when filtering possible com- pletions as part of programmable completion. nnooeexxppaanndd__ttrraannssllaattiioonn If set, bbaasshh encloses the translated results of $"..." quoting in single quotes instead of double quotes. If the string is not translated, this has no effect. nnuullllgglloobb If set, bbaasshh allows patterns which match no files (see PPaatthhnnaammee EExxppaannssiioonn in _b_a_s_h_(_1_)) to expand to a null string, rather than themselves. ppaattssuubb__rreeppllaacceemmeenntt If set, bbaasshh expands occurrences of && in the replacement string of pattern substitution to the text matched by the pattern, as described under PPaarraammeetteerr EExxppaannssiioonn in _b_a_s_h_(_1_). This option is enabled by default. pprrooggccoommpp If set, the programmable completion facilities (see PPrroo-- ggrraammmmaabbllee CCoommpplleettiioonn in _b_a_s_h_(_1_)) are enabled. This op- tion is enabled by default. pprrooggccoommpp__aalliiaass If set, and programmable completion is enabled, bbaasshh treats a command name that doesn't have any completions as a possible alias and attempts alias expansion. If it has an alias, bbaasshh attempts programmable completion us- ing the command word resulting from the expanded alias. pprroommppttvvaarrss If set, prompt strings undergo parameter expansion, com- mand substitution, arithmetic expansion, and quote re- moval after being expanded as described in PPRROOMMPPTTIINNGG in _b_a_s_h_(_1_). This option is enabled by default. rreessttrriicctteedd__sshheellll The shell sets this option if it is started in re- stricted mode (see RREESSTTRRIICCTTEEDD SSHHEELLLL in _b_a_s_h_(_1_)). The value may not be changed. This is not reset when the startup files are executed, allowing the startup files to discover whether or not a shell is restricted. sshhiifftt__vveerrbboossee If set, the sshhiifftt builtin prints an error message when the shift count exceeds the number of positional parame- ters. ssoouurrcceeppaatthh If set, the .. (ssoouurrccee) builtin uses the value of PPAATTHH to find the directory containing the file supplied as an argument. This option is enabled by default. vvaarrrreeddiirr__cclloossee If set, the shell automatically closes file descriptors assigned using the _{_v_a_r_n_a_m_e_} redirection syntax (see RREE-- DDIIRREECCTTIIOONN in _b_a_s_h_(_1_)) instead of leaving them open when the command completes. xxppgg__eecchhoo If set, the eecchhoo builtin expands backslash-escape se- quences by default. ssuussppeenndd [--ff] Suspend the execution of this shell until it receives a SSIIGGCCOONNTT signal. A login shell, or a shell without job control enabled, cannot be suspended; the --ff option can be used to override this and force the suspension. The return status is 0 unless the shell is a login shell or job control is not enabled and --ff is not supplied. tteesstt _e_x_p_r [[ _e_x_p_r ]] Return a status of 0 (true) or 1 (false) depending on the evalu- ation of the conditional expression _e_x_p_r. Each operator and op- erand must be a separate argument. Expressions are composed of the primaries described in _b_a_s_h_(_1_) under CCOONNDDIITTIIOONNAALL EEXXPPRREESS-- SSIIOONNSS. tteesstt does not accept any options, nor does it accept and ignore an argument of ---- as signifying the end of options. Expressions may be combined using the following operators, listed in decreasing order of precedence. The evaluation de- pends on the number of arguments; see below. Operator prece- dence is used when there are five or more arguments. !! _e_x_p_r True if _e_x_p_r is false. (( _e_x_p_r )) Returns the value of _e_x_p_r. This may be used to override the normal precedence of operators. _e_x_p_r_1 -aa _e_x_p_r_2 True if both _e_x_p_r_1 and _e_x_p_r_2 are true. _e_x_p_r_1 -oo _e_x_p_r_2 True if either _e_x_p_r_1 or _e_x_p_r_2 is true. tteesstt and [[ evaluate conditional expressions using a set of rules based on the number of arguments. 0 arguments The expression is false. 1 argument The expression is true if and only if the argument is not null. 2 arguments If the first argument is !!, the expression is true if and only if the second argument is null. If the first argu- ment is one of the unary conditional operators listed in _b_a_s_h_(_1_) under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, the expression is true if the unary test is true. If the first argument is not a valid unary conditional operator, the expression is false. 3 arguments The following conditions are applied in the order listed. If the second argument is one of the binary conditional operators listed in _b_a_s_h_(_1_) under CCOONNDDIITTIIOONNAALL EEXXPPRREESS-- SSIIOONNSS, the result of the expression is the result of the binary test using the first and third arguments as oper- ands. The --aa and --oo operators are considered binary op- erators when there are three arguments. If the first ar- gument is !!, the value is the negation of the two-argu- ment test using the second and third arguments. If the first argument is exactly (( and the third argument is ex- actly )), the result is the one-argument test of the sec- ond argument. Otherwise, the expression is false. 4 arguments The following conditions are applied in the order listed. If the first argument is !!, the result is the negation of the three-argument expression composed of the remaining arguments. the two-argument test using the second and third arguments. If the first argument is exactly (( and the fourth argument is exactly )), the result is the two- argument test of the second and third arguments. Other- wise, the expression is parsed and evaluated according to precedence using the rules listed above. 5 or more arguments The expression is parsed and evaluated according to precedence using the rules listed above. When used with tteesstt or [[, the << and >> operators sort lexico- graphically using ASCII ordering. ttiimmeess Print the accumulated user and system times for the shell and for processes run from the shell. The return status is 0. ttrraapp [--llpp] [[_a_r_g] _s_i_g_s_p_e_c ...] The command _a_r_g is to be read and executed when the shell re- ceives signal(s) _s_i_g_s_p_e_c. If _a_r_g is absent (and there is a sin- gle _s_i_g_s_p_e_c) or --, each specified signal is reset to its origi- nal disposition (the value it had upon entrance to the shell). If _a_r_g is the null string the signal specified by each _s_i_g_s_p_e_c is ignored by the shell and by the commands it invokes. If _a_r_g is not present and --pp has been supplied, then the trap commands associated with each _s_i_g_s_p_e_c are displayed. If no arguments are supplied or if only --pp is given, ttrraapp prints the list of com- mands associated with each signal. The --ll option causes the shell to print a list of signal names and their corresponding numbers. Each _s_i_g_s_p_e_c is either a signal name defined in <_s_i_g_- _n_a_l_._h>, or a signal number. Signal names are case insensitive and the SSIIGG prefix is optional. If a _s_i_g_s_p_e_c is EEXXIITT (0) the command _a_r_g is executed on exit from the shell. If a _s_i_g_s_p_e_c is DDEEBBUUGG, the command _a_r_g is exe- cuted before every _s_i_m_p_l_e _c_o_m_m_a_n_d, _f_o_r command, _c_a_s_e command, _s_e_l_e_c_t command, every arithmetic _f_o_r command, and before the first command executes in a shell function (see SSHHEELLLL GGRRAAMMMMAARR in _b_a_s_h_(_1_)). Refer to the description of the eexxttddeebbuugg option to the sshhoopptt builtin for details of its effect on the DDEEBBUUGG trap. If a _s_i_g_s_p_e_c is RREETTUURRNN, the command _a_r_g is executed each time a shell function or a script executed with the .. or ssoouurrccee builtins finishes executing. If a _s_i_g_s_p_e_c is EERRRR, the command _a_r_g is executed whenever a pipeline (which may consist of a single simple command), a list, or a compound command returns a non-zero exit status, subject to the following conditions. The EERRRR trap is not executed if the failed command is part of the command list immediately following a wwhhiillee or uunnttiill keyword, part of the test in an _i_f statement, part of a command executed in a &&&& or |||| list except the command following the final &&&& or ||||, any command in a pipeline but the last, or if the command's return value is being inverted using !!. These are the same conditions obeyed by the eerrrreexxiitt (--ee) op- tion. Signals ignored upon entry to the shell cannot be trapped or re- set. Trapped signals that are not being ignored are reset to their original values in a subshell or subshell environment when one is created. The return status is false if any _s_i_g_s_p_e_c is invalid; otherwise ttrraapp returns true. ttyyppee [--aaffttppPP] _n_a_m_e [_n_a_m_e ...] With no options, indicate how each _n_a_m_e would be interpreted if used as a command name. If the --tt option is used, ttyyppee prints a string which is one of _a_l_i_a_s, _k_e_y_w_o_r_d, _f_u_n_c_t_i_o_n, _b_u_i_l_t_i_n, or _f_i_l_e if _n_a_m_e is an alias, shell reserved word, function, builtin, or disk file, respectively. If the _n_a_m_e is not found, then nothing is printed, and an exit status of false is re- turned. If the --pp option is used, ttyyppee either returns the name of the disk file that would be executed if _n_a_m_e were specified as a command name, or nothing if ``type -t name'' would not re- turn _f_i_l_e. The --PP option forces a PPAATTHH search for each _n_a_m_e, even if ``type -t name'' would not return _f_i_l_e. If a command is hashed, --pp and --PP print the hashed value, which is not necessar- ily the file that appears first in PPAATTHH. If the --aa option is used, ttyyppee prints all of the places that contain an executable named _n_a_m_e. This includes aliases and functions, if and only if the --pp option is not also used. The table of hashed commands is not consulted when using --aa. The --ff option suppresses shell function lookup, as with the ccoommmmaanndd builtin. ttyyppee returns true if all of the arguments are found, false if any are not found. uulliimmiitt [--HHSS] --aa uulliimmiitt [--HHSS] [--bbccddeeffiikkllmmnnppqqrrssttuuvvxxPPRRTT [_l_i_m_i_t]] Provides control over the resources available to the shell and to processes started by it, on systems that allow such control. The --HH and --SS options specify that the hard or soft limit is set for the given resource. A hard limit cannot be increased by a non-root user once it is set; a soft limit may be increased up to the value of the hard limit. If neither --HH nor --SS is speci- fied, both the soft and hard limits are set. The value of _l_i_m_i_t can be a number in the unit specified for the resource or one of the special values hhaarrdd, ssoofftt, or uunnlliimmiitteedd, which stand for the current hard limit, the current soft limit, and no limit, re- spectively. If _l_i_m_i_t is omitted, the current value of the soft limit of the resource is printed, unless the --HH option is given. When more than one resource is specified, the limit name and unit, if appropriate, are printed before the value. Other op- tions are interpreted as follows: --aa All current limits are reported; no limits are set --bb The maximum socket buffer size --cc The maximum size of core files created --dd The maximum size of a process's data segment --ee The maximum scheduling priority ("nice") --ff The maximum size of files written by the shell and its children --ii The maximum number of pending signals --kk The maximum number of kqueues that may be allocated --ll The maximum size that may be locked into memory --mm The maximum resident set size (many systems do not honor this limit) --nn The maximum number of open file descriptors (most systems do not allow this value to be set) --pp The pipe size in 512-byte blocks (this may not be set) --qq The maximum number of bytes in POSIX message queues --rr The maximum real-time scheduling priority --ss The maximum stack size --tt The maximum amount of cpu time in seconds --uu The maximum number of processes available to a single user --vv The maximum amount of virtual memory available to the shell and, on some systems, to its children --xx The maximum number of file locks --PP The maximum number of pseudoterminals --RR The maximum time a real-time process can run before blocking, in microseconds --TT The maximum number of threads If _l_i_m_i_t is given, and the --aa option is not used, _l_i_m_i_t is the new value of the specified resource. If no option is given, then --ff is assumed. Values are in 1024-byte increments, except for --tt, which is in seconds; --RR, which is in microseconds; --pp, which is in units of 512-byte blocks; --PP, --TT, --bb, --kk, --nn, and --uu, which are unscaled values; and, when in posix mode, --cc and --ff, which are in 512-byte increments. The return status is 0 unless an invalid option or argument is supplied, or an error occurs while setting a new limit. uummaasskk [--pp] [--SS] [_m_o_d_e] The user file-creation mask is set to _m_o_d_e. If _m_o_d_e begins with a digit, it is interpreted as an octal number; otherwise it is interpreted as a symbolic mode mask similar to that accepted by _c_h_m_o_d(1). If _m_o_d_e is omitted, the current value of the mask is printed. The --SS option causes the mask to be printed in sym- bolic form; the default output is an octal number. If the --pp option is supplied, and _m_o_d_e is omitted, the output is in a form that may be reused as input. The return status is 0 if the mode was successfully changed or if no _m_o_d_e argument was supplied, and false otherwise. uunnaalliiaass [-aa] [_n_a_m_e ...] Remove each _n_a_m_e from the list of defined aliases. If --aa is supplied, all alias definitions are removed. The return value is true unless a supplied _n_a_m_e is not a defined alias. uunnsseett [-ffvv] [-nn] [_n_a_m_e ...] For each _n_a_m_e, remove the corresponding variable or function. If the --vv option is given, each _n_a_m_e refers to a shell variable, and that variable is removed. Read-only variables may not be unset. If --ff is specified, each _n_a_m_e refers to a shell func- tion, and the function definition is removed. If the --nn option is supplied, and _n_a_m_e is a variable with the _n_a_m_e_r_e_f attribute, _n_a_m_e will be unset rather than the variable it references. --nn has no effect if the --ff option is supplied. If no options are supplied, each _n_a_m_e refers to a variable; if there is no vari- able by that name, a function with that name, if any, is unset. Each unset variable or function is removed from the environment passed to subsequent commands. If any of BBAASSHH__AALLIIAASSEESS, BBAASSHH__AARRGGVV00, BBAASSHH__CCMMDDSS, BBAASSHH__CCOOMMMMAANNDD, BBAASSHH__SSUUBBSSHHEELLLL, BBAASSHHPPIIDD, CCOOMMPP__WWOORRDDBBRREEAAKKSS, DDIIRRSSTTAACCKK, EEPPOOCCHHRREEAALLTTIIMMEE, EEPPOOCCHHSSEECCOONNDDSS, FFUUNNCC-- NNAAMMEE, GGRROOUUPPSS, HHIISSTTCCMMDD, LLIINNEENNOO, RRAANNDDOOMM, SSEECCOONNDDSS, or SSRRAANNDDOOMM are unset, they lose their special properties, even if they are sub- sequently reset. The exit status is true unless a _n_a_m_e is read- only or may not be unset. wwaaiitt [--ffnn] [--pp _v_a_r_n_a_m_e] [_i_d _._._.] Wait for each specified child process and return its termination status. Each _i_d may be a process ID or a job specification; if a job spec is given, all processes in that job's pipeline are waited for. If _i_d is not given, wwaaiitt waits for all running background jobs and the last-executed process substitution, if its process id is the same as $$!!, and the return status is zero. If the --nn option is supplied, wwaaiitt waits for a single job from the list of _i_ds or, if no _i_ds are supplied, any job, to complete and returns its exit status. If none of the supplied arguments is a child of the shell, or if no arguments are supplied and the shell has no unwaited-for children, the exit status is 127. If the --pp option is supplied, the process or job identifier of the job for which the exit status is returned is assigned to the variable _v_a_r_n_a_m_e named by the option argument. The variable will be unset initially, before any assignment. This is useful only when the --nn option is supplied. Supplying the --ff option, when job control is enabled, forces wwaaiitt to wait for _i_d to ter- minate before returning its status, instead of returning when it changes status. If _i_d specifies a non-existent process or job, the return status is 127. If wwaaiitt is interrupted by a signal, the return status will be greater than 128, as described under SSIIGGNNAALLSS in _b_a_s_h_(_1_). Otherwise, the return status is the exit status of the last process or job waited for. SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE Bash-4.0 introduced the concept of a _s_h_e_l_l _c_o_m_p_a_t_i_b_i_l_i_t_y _l_e_v_e_l, speci- fied as a set of options to the shopt builtin ( ccoommppaatt3311, ccoommppaatt3322, ccoommppaatt4400, ccoommppaatt4411, and so on). There is only one current compatibil- ity level -- each option is mutually exclusive. The compatibility level is intended to allow users to select behavior from previous ver- sions that is incompatible with newer versions while they migrate scripts to use current features and behavior. It's intended to be a temporary solution. This section does not mention behavior that is standard for a particu- lar version (e.g., setting ccoommppaatt3322 means that quoting the rhs of the regexp matching operator quotes special regexp characters in the word, which is default behavior in bash-3.2 and subsequent versions). If a user enables, say, ccoommppaatt3322, it may affect the behavior of other compatibility levels up to and including the current compatibility level. The idea is that each compatibility level controls behavior that changed in that version of bbaasshh, but that behavior may have been present in earlier versions. For instance, the change to use locale- based comparisons with the [[[[ command came in bash-4.1, and earlier versions used ASCII-based comparisons, so enabling ccoommppaatt3322 will enable ASCII-based comparisons as well. That granularity may not be suffi- cient for all uses, and as a result users should employ compatibility levels carefully. Read the documentation for a particular feature to find out the current behavior. Bash-4.3 introduced a new shell variable: BBAASSHH__CCOOMMPPAATT. The value as- signed to this variable (a decimal version number like 4.2, or an inte- ger corresponding to the ccoommppaatt_N_N option, like 42) determines the com- patibility level. Starting with bash-4.4, Bash has begun deprecating older compatibility levels. Eventually, the options will be removed in favor of BBAASSHH__CCOOMM-- PPAATT. Bash-5.0 is the final version for which there will be an individual shopt option for the previous version. Users should use BBAASSHH__CCOOMMPPAATT on bash-5.0 and later versions. The following table describes the behavior changes controlled by each compatibility level setting. The ccoommppaatt_N_N tag is used as shorthand for setting the compatibility level to _N_N using one of the following mecha- nisms. For versions prior to bash-5.0, the compatibility level may be set using the corresponding ccoommppaatt_N_N shopt option. For bash-4.3 and later versions, the BBAASSHH__CCOOMMPPAATT variable is preferred, and it is re- quired for bash-5.1 and later versions. ccoommppaatt3311 +o quoting the rhs of the [[[[ command's regexp matching oper- ator (=~) has no special effect ccoommppaatt3322 +o interrupting a command list such as "a ; b ; c" causes the execution of the next command in the list (in bash-4.0 and later versions, the shell acts as if it re- ceived the interrupt, so interrupting one command in a list aborts the execution of the entire list) ccoommppaatt4400 +o the << and >> operators to the [[[[ command do not consider the current locale when comparing strings; they use ASCII ordering. Bash versions prior to bash-4.1 use ASCII col- lation and _s_t_r_c_m_p(3); bash-4.1 and later use the current locale's collation sequence and _s_t_r_c_o_l_l(3). ccoommppaatt4411 +o in _p_o_s_i_x mode, ttiimmee may be followed by options and still be recognized as a reserved word (this is POSIX interpre- tation 267) +o in _p_o_s_i_x mode, the parser requires that an even number of single quotes occur in the _w_o_r_d portion of a double- quoted parameter expansion and treats them specially, so that characters within the single quotes are considered quoted (this is POSIX interpretation 221) ccoommppaatt4422 +o the replacement string in double-quoted pattern substitu- tion does not undergo quote removal, as it does in ver- sions after bash-4.2 +o in posix mode, single quotes are considered special when expanding the _w_o_r_d portion of a double-quoted parameter expansion and can be used to quote a closing brace or other special character (this is part of POSIX interpre- tation 221); in later versions, single quotes are not special within double-quoted word expansions ccoommppaatt4433 +o the shell does not print a warning message if an attempt is made to use a quoted compound assignment as an argu- ment to declare (e.g., declare -a foo='(1 2)'). Later versions warn that this usage is deprecated +o word expansion errors are considered non-fatal errors that cause the current command to fail, even in posix mode (the default behavior is to make them fatal errors that cause the shell to exit) +o when executing a shell function, the loop state (while/until/etc.) is not reset, so bbrreeaakk or ccoonnttiinnuuee in that function will break or continue loops in the calling context. Bash-4.4 and later reset the loop state to pre- vent this ccoommppaatt4444 +o the shell sets up the values used by BBAASSHH__AARRGGVV and BBAASSHH__AARRGGCC so they can expand to the shell's positional parameters even if extended debugging mode is not enabled +o a subshell inherits loops from its parent context, so bbrreeaakk or ccoonnttiinnuuee will cause the subshell to exit. Bash-5.0 and later reset the loop state to prevent the exit +o variable assignments preceding builtins like eexxppoorrtt and rreeaaddoonnllyy that set attributes continue to affect variables with the same name in the calling environment even if the shell is not in posix mode ccoommppaatt5500 +o Bash-5.1 changed the way $$RRAANNDDOOMM is generated to intro- duce slightly more randomness. If the shell compatibility level is set to 50 or lower, it reverts to the method from bash-5.0 and previous versions, so seeding the ran- dom number generator by assigning a value to RRAANNDDOOMM will produce the same sequence as in bash-5.0 +o If the command hash table is empty, bash versions prior to bash-5.1 printed an informational message to that ef- fect, even when producing output that can be reused as input. Bash-5.1 suppresses that message when the --ll op- tion is supplied. ccoommppaatt5511 +o The uunnsseett builtin treats attempts to unset array sub- scripts @@ and ** differently depending on whether the ar- ray is indexed or associative, and differently than in previous versions. SSEEEE AALLSSOO bash(1), sh(1) GNU Bash 5.2 2021 November 22 BASH_BUILTINS(1)