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diff --git a/runtime/doc/usr_29.txt b/runtime/doc/usr_29.txt new file mode 100644 index 0000000..a534c6f --- /dev/null +++ b/runtime/doc/usr_29.txt @@ -0,0 +1,614 @@ +*usr_29.txt* For Vim version 9.1. Last change: 2022 Mar 13 + + VIM USER MANUAL - by Bram Moolenaar + + Moving through programs + + +The creator of Vim is a computer programmer. It's no surprise that Vim +contains many features to aid in writing programs. Jump around to find where +identifiers are defined and used. Preview declarations in a separate window. +There is more in the next chapter. + +|29.1| Using tags +|29.2| The preview window +|29.3| Moving through a program +|29.4| Finding global identifiers +|29.5| Finding local identifiers + + Next chapter: |usr_30.txt| Editing programs + Previous chapter: |usr_28.txt| Folding +Table of contents: |usr_toc.txt| + +============================================================================== +*29.1* Using tags + +What is a tag? It is a location where an identifier is defined. An example +is a function definition in a C or C++ program. A list of tags is kept in a +tags file. This can be used by Vim to directly jump from any place to the +tag, the place where an identifier is defined. + To generate the tags file for all C files in the current directory, use the +following command: > + + ctags *.c + +"ctags" is a separate program. Most Unix systems already have it installed. +If you do not have it yet, you can find Universal/Exuberant ctags at: + http://ctags.io ~ + http://ctags.sf.net ~ + +Universal ctags is preferred, Exuberant ctags is no longer being developed. + +Now when you are in Vim and you want to go to a function definition, you can +jump to it by using the following command: > + + :tag startlist + +This command will find the function "startlist" even if it is in another file. + The CTRL-] command jumps to the tag of the word that is under the cursor. +This makes it easy to explore a tangle of C code. Suppose, for example, that +you are in the function "write_block". You can see that it calls +"write_line". But what does "write_line" do? By placing the cursor on the +call to "write_line" and pressing CTRL-], you jump to the definition of this +function. + The "write_line" function calls "write_char". You need to figure out what +it does. So you position the cursor over the call to "write_char" and press +CTRL-]. Now you are at the definition of "write_char". + + +-------------------------------------+ + |void write_block(char **s; int cnt) | + |{ | + | int i; | + | for (i = 0; i < cnt; ++i) | + | write_line(s[i]); | + |} | | + +-----------|-------------------------+ + | + CTRL-] | + | +----------------------------+ + +--> |void write_line(char *s) | + |{ | + | while (*s != 0) | + | write_char(*s++); | + |} | | + +--------|-------------------+ + | + CTRL-] | + | +------------------------------------+ + +--> |void write_char(char c) | + |{ | + | putchar((int)(unsigned char)c); | + |} | + +------------------------------------+ + +The ":tags" command shows the list of tags that you traversed through: + + :tags + # TO tag FROM line in file/text ~ + 1 1 write_line 8 write_block.c ~ + 2 1 write_char 7 write_line.c ~ + > ~ +> +Now to go back. The CTRL-T command goes to the preceding tag. In the example +above you get back to the "write_line" function, in the call to "write_char". + This command takes a count argument that indicates how many tags to jump +back. You have gone forward, and now back. Let's go forward again. The +following command goes to the tag on top of the list: > + + :tag + +You can prefix it with a count and jump forward that many tags. For example: +":3tag". CTRL-T also can be preceded with a count. + These commands thus allow you to go down a call tree with CTRL-] and back +up again with CTRL-T. Use ":tags" to find out where you are. + + +SPLIT WINDOWS + +The ":tag" command replaces the file in the current window with the one +containing the new function. But suppose you want to see not only the old +function but also the new one? You can split the window using the ":split" +command followed by the ":tag" command. Vim has a shorthand command that does +both: > + :stag tagname + +To split the current window and jump to the tag under the cursor use this +command: > + + CTRL-W ] + +If a count is specified, the new window will be that many lines high. + + +MORE TAGS FILES + +When you have files in many directories, you can create a tags file in each of +them. Vim will then only be able to jump to tags within that directory. + To find more tags files, set the 'tags' option to include all the relevant +tags files. Example: > + + :set tags=./tags,./../tags,./*/tags + +This finds a tags file in the same directory as the current file, one +directory level higher and in all subdirectories. + This is quite a number of tags files, but it may still not be enough. For +example, when editing a file in "~/proj/src", you will not find the tags file +"~/proj/sub/tags". For this situation Vim offers to search a whole directory +tree for tags files. Example: > + + :set tags=~/proj/**/tags + + +ONE TAGS FILE + +When Vim has to search many places for tags files, you can hear the disk +rattling. It may get a bit slow. In that case it's better to spend this +time while generating one big tags file. You might do this overnight. + This requires the Universal or Exuberant ctags program, mentioned above. +It offers an argument to search a whole directory tree: > + + cd ~/proj + ctags -R . + +The nice thing about this is that Universal/Exuberant ctags recognizes various +file types. Thus this doesn't work just for C and C++ programs, also for +Eiffel and even Vim scripts. See the ctags documentation to tune this. + Now you only need to tell Vim where your big tags file is: > + + :set tags=~/proj/tags + + +MULTIPLE MATCHES + +When a function is defined multiple times (or a method in several classes), +the ":tag" command will jump to the first one. If there is a match in the +current file, that one is used first. + You can now jump to other matches for the same tag with: > + + :tnext + +Repeat this to find further matches. If there are many, you can select which +one to jump to: > + + :tselect tagname + +Vim will present you with a list of choices: + + # pri kind tag file ~ + 1 F f mch_init os_amiga.c ~ + mch_init() ~ + 2 F f mch_init os_mac.c ~ + mch_init() ~ + 3 F f mch_init os_msdos.c ~ + mch_init(void) ~ + 4 F f mch_init os_riscos.c ~ + mch_init() ~ + Enter nr of choice (<CR> to abort): ~ + +You can now enter the number (in the first column) of the match that you would +like to jump to. The information in the other columns give you a good idea of +where the match is defined. + +To move between the matching tags, these commands can be used: + + :tfirst go to first match + :[count]tprevious go to [count] previous match + :[count]tnext go to [count] next match + :tlast go to last match + +If [count] is omitted then one is used. + + +GUESSING TAG NAMES + +Command line completion is a good way to avoid typing a long tag name. Just +type the first bit and press <Tab>: > + + :tag write_<Tab> + +You will get the first match. If it's not the one you want, press <Tab> until +you find the right one. + Sometimes you only know part of the name of a function. Or you have many +tags that start with the same string, but end differently. Then you can tell +Vim to use a pattern to find the tag. + Suppose you want to jump to a tag that contains "block". First type +this: > + + :tag /block + +Now use command line completion: press <Tab>. Vim will find all tags that +contain "block" and use the first match. + The "/" before a tag name tells Vim that what follows is not a literal tag +name, but a pattern. You can use all the items for search patterns here. For +example, suppose you want to select a tag that starts with "write_": > + + :tselect /^write_ + +The "^" specifies that the tag starts with "write_". Otherwise it would also +be found halfway a tag name. Similarly "$" at the end makes sure the pattern +matches until the end of a tag. + + +A TAGS BROWSER + +Since CTRL-] takes you to the definition of the identifier under the cursor, +you can use a list of identifier names as a table of contents. Here is an +example. + First create a list of identifiers (this requires Universal or Exuberant +ctags): > + + ctags --c-types=f -f functions *.c + +Now start Vim without a file, and edit this file in Vim, in a vertically split +window: > + + vim + :vsplit functions + +The window contains a list of all the functions. There is some more stuff, +but you can ignore that. Do ":setlocal ts=99" to clean it up a bit. + In this window, define a mapping: > + + :nnoremap <buffer> <CR> 0ye<C-W>w:tag <C-R>"<CR> + +Move the cursor to the line that contains the function you want to go to. +Now press <Enter>. Vim will go to the other window and jump to the selected +function. + + +RELATED ITEMS + +To make case in tag names be ignored, you can set 'ignorecase' while leaving +'tagcase' as "followic", or set 'tagcase' to "ignore". + +The 'tagbsearch' option tells if the tags file is sorted or not. The default +is to assume a sorted tags file, which makes a tags search a lot faster, but +doesn't work if the tags file isn't sorted. + +The 'taglength' option can be used to tell Vim the number of significant +characters in a tag. + +Cscope is a free program. It does not only find places where an identifier is +declared, but also where it is used. See |cscope|. + +============================================================================== +*29.2* The preview window + +When you edit code that contains a function call, you need to use the correct +arguments. To know what values to pass you can look at how the function is +defined. The tags mechanism works very well for this. Preferably the +definition is displayed in another window. For this the preview window can be +used. + To open a preview window to display the function "write_char": > + + :ptag write_char + +Vim will open a window, and jumps to the tag "write_char". Then it takes you +back to the original position. Thus you can continue typing without the need +to use a CTRL-W command. + If the name of a function appears in the text, you can get its definition +in the preview window with: > + + CTRL-W } + +There is a script that automatically displays the text where the word under +the cursor was defined. See |CursorHold-example|. + +To close the preview window use this command: > + + :pclose + +To edit a specific file in the preview window, use ":pedit". This can be +useful to edit a header file, for example: > + + :pedit defs.h + +Finally, ":psearch" can be used to find a word in the current file and any +included files and display the match in the preview window. This is +especially useful when using library functions, for which you do not have a +tags file. Example: > + + :psearch popen + +This will show the "stdio.h" file in the preview window, with the function +prototype for popen(): + + FILE *popen __P((const char *, const char *)); ~ + +You can specify the height of the preview window, when it is opened, with the +'previewheight' option. + +============================================================================== +*29.3* Moving through a program + +Since a program is structured, Vim can recognize items in it. Specific +commands can be used to move around. + C programs often contain constructs like this: + + #ifdef USE_POPEN ~ + fd = popen("ls", "r") ~ + #else ~ + fd = fopen("tmp", "w") ~ + #endif ~ + +But then much longer, and possibly nested. Position the cursor on the +"#ifdef" and press %. Vim will jump to the "#else". Pressing % again takes +you to the "#endif". Another % takes you to the "#ifdef" again. + When the construct is nested, Vim will find the matching items. This is a +good way to check if you didn't forget an "#endif". + When you are somewhere inside a "#if" - "#endif", you can jump to the start +of it with: > + + [# + +If you are not after a "#if" or "#ifdef" Vim will beep. To jump forward to +the next "#else" or "#endif" use: > + + ]# + +These two commands skip any "#if" - "#endif" blocks that they encounter. +Example: + + #if defined(HAS_INC_H) ~ + a = a + inc(); ~ + # ifdef USE_THEME ~ + a += 3; ~ + # endif ~ + set_width(a); ~ + +With the cursor in the last line, "[#" moves to the first line. The "#ifdef" +- "#endif" block in the middle is skipped. + + +MOVING IN CODE BLOCKS + +In C code blocks are enclosed in {}. These can get pretty long. To move to +the start of the outer block use the "[[" command. Use "][" to find the end. +This assumes that the "{" and "}" are in the first column. + The "[{" command moves to the start of the current block. It skips over +pairs of {} at the same level. "]}" jumps to the end. + An overview: + + function(int a) + +-> { + | if (a) + | +-> { + [[ | | for (;;) --+ + | | +-> { | + | [{ | | foo(32); | --+ + | | [{ | if (bar(a)) --+ | ]} | + +-- | +-- break; | ]} | | + | } <-+ | | ][ + +-- foobar(a) | | + } <-+ | + } <-+ + +When writing C++ or Java, the outer {} block is for the class. The next level +of {} is for a method. When somewhere inside a class use "[m" to find the +previous start of a method. "]m" finds the next start of a method. + +Additionally, "[]" moves backward to the end of a function and "]]" moves +forward to the start of the next function. The end of a function is defined +by a "}" in the first column. + + int func1(void) + { + return 1; + +----------> } + | + [] | int func2(void) + | +-> { + | [[ | if (flag) + start +-- +-- return flag; + | ][ | return 2; + | +-> } + ]] | + | int func3(void) + +----------> { + return 3; + } + +Don't forget you can also use "%" to move between matching (), {} and []. +That also works when they are many lines apart. + + +MOVING IN BRACES + +The "[(" and "])" commands work similar to "[{" and "]}", except that they +work on () pairs instead of {} pairs. +> + [( +< <-------------------------------- + <------- + if (a == b && (c == d || (e > f)) && x > y) ~ + --------------> + --------------------------------> > + ]) + +MOVING IN COMMENTS + +To move back to the start of a comment use "[/". Move forward to the end of a +comment with "]/". This only works for /* - */ comments. + + +-> +-> /* + | [/ | * A comment about --+ + [/ | +-- * wonderful life. | ]/ + | */ <-+ + | + +-- foo = bar * 3; --+ + | ]/ + /* a short comment */ <-+ + +============================================================================== +*29.4* Finding global identifiers + +You are editing a C program and wonder if a variable is declared as "int" or +"unsigned". A quick way to find this is with the "[I" command. + Suppose the cursor is on the word "column". Type: > + + [I + +Vim will list the matching lines it can find. Not only in the current file, +but also in all included files (and files included in them, etc.). The result +looks like this: + + structs.h ~ + 1: 29 unsigned column; /* column number */ ~ + +The advantage over using tags or the preview window is that included files are +searched. In most cases this results in the right declaration to be found. +Also when the tags file is out of date. Also when you don't have tags for the +included files. + However, a few things must be right for "[I" to do its work. First of all, +the 'include' option must specify how a file is included. The default value +works for C and C++. For other languages you will have to change it. + + +LOCATING INCLUDED FILES + + Vim will find included files in the places specified with the 'path' +option. If a directory is missing, some include files will not be found. You +can discover this with this command: > + + :checkpath + +It will list the include files that could not be found. Also files included +by the files that could be found. An example of the output: + + --- Included files not found in path --- ~ + <io.h> ~ + vim.h --> ~ + <functions.h> ~ + <clib/exec_protos.h> ~ + +The "io.h" file is included by the current file and can't be found. "vim.h" +can be found, thus ":checkpath" goes into this file and checks what it +includes. The "functions.h" and "clib/exec_protos.h" files, included by +"vim.h" are not found. + + Note: + Vim is not a compiler. It does not recognize "#ifdef" statements. + This means every "#include" statement is used, also when it comes + after "#if NEVER". + +To fix the files that could not be found, add a directory to the 'path' +option. A good place to find out about this is the Makefile. Look out for +lines that contain "-I" items, like "-I/usr/local/X11". To add this directory +use: > + + :set path+=/usr/local/X11 + +When there are many subdirectories, you can use the "*" wildcard. Example: > + + :set path+=/usr/*/include + +This would find files in "/usr/local/include" as well as "/usr/X11/include". + +When working on a project with a whole nested tree of included files, the "**" +items is useful. This will search down in all subdirectories. Example: > + + :set path+=/projects/invent/**/include + +This will find files in the directories: + + /projects/invent/include ~ + /projects/invent/main/include ~ + /projects/invent/main/os/include ~ + etc. + +There are even more possibilities. Check out the 'path' option for info. + If you want to see which included files are actually found, use this +command: > + + :checkpath! + +You will get a (very long) list of included files, the files they include, and +so on. To shorten the list a bit, Vim shows "(Already listed)" for files that +were found before and doesn't list the included files in there again. + + +JUMPING TO A MATCH + +"[I" produces a list with only one line of text. When you want to have a +closer look at the first item, you can jump to that line with the command: > + + [<Tab> + +You can also use "[ CTRL-I", since CTRL-I is the same as pressing <Tab>. + +The list that "[I" produces has a number at the start of each line. When you +want to jump to another item than the first one, type the number first: > + + 3[<Tab> + +Will jump to the third item in the list. Remember that you can use CTRL-O to +jump back to where you started from. + + +RELATED COMMANDS + + [i only lists the first match + ]I only lists items below the cursor + ]i only lists the first item below the cursor + + +FINDING DEFINED IDENTIFIERS + +The "[I" command finds any identifier. To find only macros, defined with +"#define" use: > + + [D + +Again, this searches in included files. The 'define' option specifies what a +line looks like that defines the items for "[D". You could change it to make +it work with other languages than C or C++. + The commands related to "[D" are: + + [d only lists the first match + ]D only lists items below the cursor + ]d only lists the first item below the cursor + +============================================================================== +*29.5* Finding local identifiers + +The "[I" command searches included files. To search in the current file only, +and jump to the first place where the word under the cursor is used: > + + gD + +Hint: Goto Definition. This command is very useful to find a variable or +function that was declared locally ("static", in C terms). Example (cursor on +"counter"): + + +-> static int counter = 0; + | + | int get_counter(void) + gD | { + | ++counter; + +-- return counter; + } + +To restrict the search even further, and look only in the current function, +use this command: > + + gd + +This will go back to the start of the current function and find the first +occurrence of the word under the cursor. Actually, it searches backwards to +an empty line above a "{" in the first column. From there it searches forward +for the identifier. Example (cursor on "idx"): + + int find_entry(char *name) + { + +-> int idx; + | + gd | for (idx = 0; idx < table_len; ++idx) + | if (strcmp(table[idx].name, name) == 0) + +-- return idx; + } + +============================================================================== + +Next chapter: |usr_30.txt| Editing programs + +Copyright: see |manual-copyright| vim:tw=78:ts=8:noet:ft=help:norl: |