The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> sys/wait.h - declarations for waiting

#### SYNOPSIS

> `#include <sys/wait.h>`

#### DESCRIPTION

> The <sys/wait.h> header shall define the following symbolic constants for use with waitpid():

> WCONTINUED
>   [XSI] Report status of continued child process.
> WNOHANG
>   Do not hang if no status is available; return immediately.
> WUNTRACED
>   Report status of stopped child process.

> The <sys/wait.h> header shall define the following macros for analysis of process status values:

> WEXITSTATUS
>   Return exit status.
> WIFCONTINUED
>   [XSI] True if child has been continued.
> WIFEXITED
>   True if child exited normally.
> WIFSIGNALED
>   True if child exited due to uncaught signal.
> WIFSTOPPED
>   True if child is currently stopped.
> WSTOPSIG
>   Return signal number that caused process to stop.
> WTERMSIG
>   Return signal number that caused process to terminate.

> The <sys/wait.h> header shall define the following symbolic constants as possible values for the options argument to waitid():

> WEXITED
>   Wait for processes that have exited.
> WNOWAIT
>   Keep the process whose status is returned in infop in a waitable state.
> WSTOPPED
>   Status is returned for any child that has stopped upon receipt of a signal.

> The [XSI] WCONTINUED and WNOHANG constants, described above for waitpid(), can also be used with waitid().

> The type idtype_t shall be defined as an enumeration type whose possible values shall include at least the following: P_ALL P_PGID P_PID

> The <sys/wait.h> header shall define the id_t and pid_t types as described in <sys/types.h>.

> The <sys/wait.h> header shall define the siginfo_t type and the sigval union as described in <signal.h>.

> Inclusion of the <sys/wait.h> header may also make visible all symbols from <signal.h>.

> The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

>     pid_t  wait(int *);
>     int    waitid(idtype_t, id_t, siginfo_t *, int);
>     pid_t  waitpid(pid_t, int *, int);

The following sections are informative.

#### APPLICATION USAGE

> None.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> <signal.h>, <sys/resource.h>, <sys/types.h>

> XSH wait, waitid

#### CHANGE HISTORY

> First released in Issue 3.

> Included for alignment with the POSIX.1-1988 standard.

#### Issue 6

> The wait3() function is removed.

#### Issue 7

> The waitid() function and symbolic constants for its options argument are moved to the Base.

> The description of the WNOHANG constant is clarified.

> The requirement for <sys/wait.h> to define the rusage structure as described in <sys/resource.h> is removed, and <sys/wait.h> is no longer allowed to make visible all symbols from <sys/resource.h>.

> POSIX.1-2008, Technical Corrigendum 2, XBD/TC2-2008/0082 [579] and XBD/TC2-2008/0083 [564] are applied.

End of informative text.

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