wait() -- System Call (libc)

Await completion of a child process
#include <sys/wait.h>
wait(statp)
int *statp;

wait() suspends  execution of  the invoking  process until a  child process
(created with fork()) terminates.  It returns the process identifier of the
terminating child  process.  If  there are no  children or if  an interrupt
occurs, it returns -1.

If  it  is  successful,  wait()  returns  the  process  identifier  of  the
terminated child process.  In addition, wait() fills in the integer pointed
to by  statp with exit-status information about  the completed process.  If
statp is NULL, wait() discards the exit-status information.

wait()  fills in  the  low byte  of  the status-information  word with  the
termination  status  of  the  child  process.   A child  process  may  have
terminated because  of a signal, because  of an exit call,  or have stopped
execution  during  ptrace().  Termination  with  exit(),  which  is  normal
completion,  gives status  0.   Other terminations  give  signal values  as
status (as defined in the article  on signal()). The 0200 bit of the status
code indicates that  a core dump was produced.  A  status of 0177 indicates
that the process is waiting for further action from ptrace().

The high byte of the returned status is the low byte of the argument to the
exit() system call.

If a parent process does not remain in existence long enough to wait() on a
child  process,   the  child   process  is   adopted  by  process   1  (the
initialization process).

Example

For an example of this system call, see the entry for msgget().

See Also

_exit(),
fork(),
ksh,
libc,
ptrace(),
signal(),
sh,
waitpid(),
wait.h
POSIX Standard, §3.2.1

© 2012 by Stephen A. Ness