WAIT(2)
NAME
wait − wait for process to terminate
SYNOPSIS
wait(status)
int *status;
wait(0)
DESCRIPTION
Wait causes its caller to delay until a signal is received or one of its child processes terminates. If any child has died since the last wait, return is immediate; if there are no children, return is immediate with the error bit set (resp. with a value of −1 returned). The normal return yields the process ID of the terminated child. In the case of several children several wait calls are needed to learn of all the deaths.
If (int)status is nonzero, the high byte of the word pointed to receives the low byte of the argument of exit when the child terminated. The low byte receives the termination status of the process. See signal(2) for a list of termination statuses (signals); 0 status indicates normal termination. A special status (0177) is returned for a stopped process which has not terminated and can be restarted. See ptrace(2). If the 0200 bit of the termination status is set, a core image of the process was produced by the system.
If the parent process terminates without waiting on its children, the initialization process (process ID = 1) inherits the children.
RETURN VALUE
If wait returns due to the receipt of a signal, a value of −1 is returned to the calling process and the 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.
DIAGNOSTICS
Wait will fail and return immediately if the following is true:
[ECHILD] The calling process has no unwaited-for child processes.
[EFAULT] The status argument points to an address outside of the process’s allocated address space.
SEE ALSO
ASSEMBLER
(wait = 7.)
sys wait
(process ID in r0)
(status in r1)
The high byte of the status is the low byte of r0 in the child at termination.