02-21-2005
Need help with SIGCHLD
Hello everybody, this is my first post on this forum. I have a program that has a child process that sleeps for 5 second and exit. I'm suppose to modify this program so that when the child exits, the parent reports the exit status of the child, so I also have to deal with SIGINT and SIGQUIT. Can someone explain to me where I should put my SIGCHLD handler? Any explanation as to how does SIGCHLD work will also be greatly appreciated. Thank you very much.
UlSky
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WAIT(2) System Calls Manual WAIT(2)
NAME
wait - wait for a process to exit
SYNOPSIS
#include <u.h>
#include <libc.h>
int wait(Waitmsg *w)
DESCRIPTION
Wait causes a process to wait for any child process (see fork(2)) to exit. It returns the pid of a child that has exited and fills in w
with more information about the child. W points to a Waitmsg, which has this structure:
typedef
struct Waitmsg
{
char pid[12]; /* of loved one */
char time[3*12]; /* of loved one & descendants */
char msg[ERRLEN];
} Waitmsg;
Pid is the child's process id. The time array contains the time the child and its descendants spent in user code, the time spent in system
calls, and the child's elapsed real time, all in units of milliseconds. All integers in a Waitmsg are formatted as right-justified textual
numbers in 11-byte fields followed by a blank. Msg contains the message that the child specified in exits(2). For a normal exit, msg[0]
is zero, otherwise msg is prefixed by the process name, a blank, the process id, and a colon.
If there are no more children to wait for, wait returns immediately, with return value -1.
SOURCE
/sys/src/libc/9syscall
SEE ALSO
fork(2), exits(2), the wait file in proc(3)
DIAGNOSTICS
Sets errstr.
WAIT(2)