wait() -- wait for process termination

SYNOPSIS

#include <sys/types.h>

#include <sys/wait.h>

pid_t wait(int *stat_loc);

The wait() function lets the calling process obtain status information about one of its child processes. If status information is available for two or more child processes, the order in which their status is reported is unspecified. If more than one thread is suspended in wait() awaiting termination of the same process, exactly one thread returns the process status at the time of the target child process termination. The other threads return -1, with errno set to ECHILD.

If the calling process sets SIGCHLD to SIG_IGN, and the process has no unwaited for children that were transformed into zombie processes, the calling thread blocks until all of the children of the process terminate, at which time wait() returns -1 with errno set to ECHILD.

If the parent process terminates without waiting for all of its child processes to terminate, the remaining child processes is assigned a new parent process ID corresponding to a system-level process.

PARAMETERS

stat_loc

Specifies the location where the child process' exit status is stored. If NULL is passed, no exit status is returned. Otherwise, the following macros defined in <sys/wait.h> can be used to evaluate the returned status:

WIFEXITED(s): Evaluates to a non-zero value if status was returned for a child process that exited normally.
WEXITSTATUS(s): If the value of WIFEXITED(s) is non-zero, this macro evaluates to the low-order 8 bits of the status argument that the child process passed to exit() or _exit(), or the value the child process returned from main().
WIFSIGNALED(s): Evaluates to a non-zero value if status was returned for a child process that terminated due to receipt of a signal that was not caught.
WTERMSIG(s): If the value of WIFSIGNALED(s) is non-zero, this macro evaluates to the number of the signal that caused the termination of the child process.
WIFCORED(s): Evaluates to a non-zero value if status was returned for a child process that terminated due to receipt of a signal that was not caught, and whose default action is to dump core.
WCOREDUMP(s): Evaluates to a non-zero value if status was returned for a child process that terminated due to receipt of a signal that was not caught, and whose default action is to dump core.; WCORESIG(s)
If the value of WIFCORED(s) is non-zero, this macro evaluates to the number of the signal that caused the termination of the child process.
WIFSTOPPED(s): Evaluates to a non-zero value if status was returned for a child process that is currently stopped.
WSTOPSIG(s): If the value of WIFSTOPPED(s) is non-zero, this macro evaluates to the number of the signal that caused the child process to stop.

RETURN VALUES

On success, wait() returns process ID of a child when the status of that child is available. Otherwise, it returns -1 and sets errno to one of the following values:

ECHILD: The process or process group specified by pid does not exist or is not a child of the calling process.
EFAULT: stat_loc is not a writable address.
EINTR: The function was interrupted by a signal. The value of the location pointed to by stat_loc is undefined.

wait()
wait for process termination

Function

SYNOPSIS

DESCRIPTION

PARAMETERS

RETURN VALUES

CONFORMANCE

MULTITHREAD SAFETY LEVEL

PORTING ISSUES

AVAILABILITY

SEE ALSO

wait() wait for process termination

Function

wait()
wait for process termination