WAIT(2) WAIT(2)
NAME
wait - wait for child process to stop or terminate
SYNOPSIS
int wait (statloc)
int *statloc;
DESCRIPTION
wait suspends the calling process until until one of the
immediate children terminates or until a child that is being
traced stops, because it has hit a break point. The wait
system call will return prematurely if a signal is received
and if a child process stopped or terminated prior to the
call on wait, return is immediate.
If stat_loc is non-zero, 16 bits of information called
status are stored in the low order 16 bits of the location
pointed to by stat_loc. Status can be used to differentiate
between stopped and terminated child processes and if the
child process terminated, status identifies the cause of
termination and passes useful information to the parent.
This is accomplished in the following manner:
If the child process stopped, the high order 8 bits of
status will contain the number of the signal that
caused the process to stop and the low order 8 bits
will be set equal to 0177.
If the child process terminated due to an exit call,
the low order 8 bits of status will be zero and the
high order 8 bits will contain the low order 8 bits of
the argument that the child process passed to exit [see
exit(2)].
If the child process terminated due to a signal, the
high order 8 bits of status will be zero and the low
order 8 bits will contain the number of the signal that
caused the termination. In addition, if the low order
seventh bit (i.e., bit 200) is set, a ``core image''
will have been produced [see signal(2)].
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WAIT(2) WAIT(2)
If a parent process terminates without waiting for its child
processes to terminate, the parent process ID of each child
process is set to 1. This means the initialization process
inherits the child processes [see intro(2)].
wait will fail and return immediately if one or more of the
following are true:
[ECHILD] The calling process has no existing
unwaited-for child processes.
SEE ALSO
exec(2), exit(2), fork(2), intro(2), pause(2), ptrace(2),
signal(2).
WARNING
wait fails and its actions are undefined if stat_loc points
to an invalid address.
See WARNING in signal(2).
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WAIT(2) WAIT(2)
DIAGNOSTICS
If wait returns due to the receipt of a signal, a value of
-1 is returned to the calling process and errno is set to
EINTR. If wait returns due to a stopped or terminated child
process, the process ID of the child is returned to the
calling process. Otherwise, a value of -1 is returned and
errno is set to indicate the error.
Page 3 May 1989