diff options
Diffstat (limited to 'man2/wait.2')
| -rw-r--r-- | man2/wait.2 | 58 |
1 files changed, 29 insertions, 29 deletions
diff --git a/man2/wait.2 b/man2/wait.2 index cbd851e..e15ca87 100644 --- a/man2/wait.2 +++ b/man2/wait.2 @@ -26,7 +26,7 @@ .\" 2005-05-10, mtk, __W* flags can't be used with waitid() .\" 2008-07-04, mtk, removed erroneous text about SA_NOCLDSTOP .\" -.TH wait 2 2023-05-03 "Linux man-pages 6.05.01" +.TH wait 2 2023-10-31 "Linux man-pages 6.7" .SH NAME wait, waitpid, waitid \- wait for process to change state .SH LIBRARY @@ -35,21 +35,21 @@ Standard C library .SH SYNOPSIS .nf .B #include <sys/wait.h> -.PP +.P .BI "pid_t wait(int *_Nullable " "wstatus" ); .BI "pid_t waitpid(pid_t " pid ", int *_Nullable " wstatus ", int " options ); -.PP +.P .BI "int waitid(idtype_t " idtype ", id_t " id \ ", siginfo_t *" infop ", int " options ); /* This is the glibc and POSIX interface; see NOTES for information on the raw system call. */ .fi -.PP +.P .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE -.PP +.P .BR waitid (): .nf Since glibc 2.26: @@ -70,7 +70,7 @@ In the case of a terminated child, performing a wait allows the system to release the resources associated with the child; if a wait is not performed, then the terminated child remains in a "zombie" state (see NOTES below). -.PP +.P If a child has already changed state, then these calls return immediately. Otherwise, they block until either a child changes state or a signal handler interrupts the call (assuming that system calls @@ -90,13 +90,13 @@ children terminates. The call .I wait(&wstatus) is equivalent to: -.PP +.P .in +4n .EX waitpid(\-1, &wstatus, 0); .EE .in -.PP +.P The .BR waitpid () system call suspends execution of the calling thread until a @@ -109,7 +109,7 @@ waits only for terminated children, but this behavior is modifiable via the .I options argument, as described below. -.PP +.P The value of .I pid can be: @@ -131,7 +131,7 @@ equal to that of the calling process at the time of the call to meaning wait for the child whose process ID is equal to the value of .IR pid . -.PP +.P The value of .I options is an OR of zero or more of the following constants: @@ -151,9 +151,9 @@ even if this option is not specified. .BR WCONTINUED " (since Linux 2.6.10)" also return if a stopped child has been resumed by delivery of .BR SIGCONT . -.PP +.P (For Linux-only options, see below.) -.PP +.P If .I wstatus is not NULL, @@ -233,7 +233,7 @@ The .BR waitid () system call (available since Linux 2.6.9) provides more precise control over which child state changes to wait for. -.PP +.P The .I idtype and @@ -266,7 +266,7 @@ as the caller's process group at the time of the call. Wait for any child; .I id is ignored. -.PP +.P The child state changes to wait for are specified by ORing one or more of the following flags in .IR options : @@ -281,7 +281,7 @@ Wait for children that have been stopped by delivery of a signal. Wait for (previously stopped) children that have been resumed by delivery of .BR SIGCONT . -.PP +.P The following flags may additionally be ORed in .IR options : .TP @@ -292,7 +292,7 @@ As for .B WNOWAIT Leave the child in a waitable state; a later wait call can be used to again retrieve the child status information. -.PP +.P Upon successful return, .BR waitid () fills in the following fields of the @@ -337,7 +337,7 @@ Set to one of: .B CLD_CONTINUED (child continued by .BR SIGCONT ). -.PP +.P If .B WNOHANG was specified in @@ -355,7 +355,7 @@ waitable state, zero out the .I si_pid field before the call and check for a nonzero value in this field after the call returns. -.PP +.P POSIX.1-2008 Technical Corrigendum 1 (2013) adds the requirement that when .B WNOHANG is specified in @@ -382,7 +382,7 @@ not all implementations follow the POSIX.1 specification on this point. .BR wait (): on success, returns the process ID of the terminated child; on failure, \-1 is returned. -.PP +.P .BR waitpid (): on success, returns the process ID of the child whose state has changed; if @@ -391,7 +391,7 @@ was specified and one or more child(ren) specified by .I pid exist, but have not yet changed state, then 0 is returned. On failure, \-1 is returned. -.PP +.P .BR waitid (): returns 0 on success or if @@ -404,7 +404,7 @@ on failure, \-1 is returned. .\" returns the PID of the child. Either this is a bug, or it is intended .\" behavior that needs to be documented. See my Jan 2009 LKML mail .\" "waitid() return value strangeness when infop is NULL". -.PP +.P On failure, each of these calls sets .I errno to indicate the error. @@ -465,7 +465,7 @@ is equal to .BR wait () is actually a library function that (in glibc) is implemented as a call to .BR wait4 (2). -.PP +.P On some architectures, there is no .BR waitpid () system call; @@ -473,7 +473,7 @@ system call; instead, this interface is implemented via a C library wrapper function that calls .BR wait4 (2). -.PP +.P The raw .BR waitid () system call takes a fifth argument, of type @@ -507,7 +507,7 @@ are adopted by operation); .BR init (1) automatically performs a wait to remove the zombies. -.PP +.P POSIX.1-2001 specifies that if the disposition of .B SIGCHLD is set to @@ -536,7 +536,7 @@ Note that even though the default disposition of is "ignore", explicitly setting the disposition to .B SIG_IGN results in different treatment of zombie process children.) -.PP +.P Linux 2.6 conforms to the POSIX requirements. However, Linux 2.4 (and earlier) does not: if a @@ -565,7 +565,7 @@ of another thread, even when the latter belongs to the same thread group. However, POSIX prescribes such functionality, and since Linux 2.4 a thread can, and by default will, wait on children of other threads in the same thread group. -.PP +.P The following Linux-specific .I options are for use with children created using @@ -596,7 +596,7 @@ type ("clone" or "non-clone"). Do not wait for children of other threads in the same thread group. This was the default before Linux 2.4. -.PP +.P Since Linux 4.7, .\" commit bf959931ddb88c4e4366e96dd22e68fa0db9527c .\" prevents cases where an unreapable zombie is created if @@ -636,9 +636,9 @@ using the integer supplied on the command line as the exit status. The parent process executes a loop that monitors the child using .BR waitpid (), and uses the W*() macros described above to analyze the wait status value. -.PP +.P The following shell session demonstrates the use of the program: -.PP +.P .in +4n .EX .RB "$" " ./a.out &" |