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#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
#include "ipc_sync.h"
#include "warnp.h"
#include "daemonize.h"
/* Write the process' pid to a file called ${spid}. */
static int
writepid(const char * spid)
{
FILE * f;
/* Write our pid to a file. */
if ((f = fopen(spid, "w")) == NULL) {
warnp("fopen(%s)", spid);
goto err0;
}
if (fprintf(f, "%jd", (intmax_t)getpid()) < 0) {
warnp("fprintf");
goto err1;
}
if (fclose(f)) {
warnp("fclose");
goto err0;
}
/* Success! */
return (0);
err1:
if (fclose(f))
warnp("fclose");
err0:
/* Failure! */
return (-1);
}
/**
* daemonize(spid):
* Daemonize and write the process ID in decimal to a file named ${spid}.
* The parent process will exit only after the child has written its pid.
* On success, the child will return 0; on failure, the parent will return
* -1.
*/
int
daemonize(const char * spid)
{
struct ipc_sync * IS;
/*
* Create a pipe for the child to notify the parent when it has
* finished daemonizing.
*/
if ((IS = ipc_sync_init()) == NULL)
goto err0;
/*
* Fork into the parent process (which waits for a poke and exits)
* and the child process (which keeps going).
*/
switch (fork()) {
case -1:
/* Fork failed. */
warnp("fork");
goto err1;
case 0:
/* In child process. */
break;
default:
/* In parent process; wait for the child to start. */
if (ipc_sync_wait(IS))
goto err1;
/*
* Free resources associated with ${IS}. These would be
* released by the following _exit(), but we're explicitly
* releasing them for the benefit of leak checkers.
*/
if (ipc_sync_done(IS))
goto err0;
/* We have been poked by the child. Exit. */
_exit(0);
}
/* Set ourselves to be a session leader. */
if (setsid() == -1) {
warnp("setsid");
goto die;
}
/* Write out our pid file. */
if (writepid(spid))
goto die;
/* Tell the parent that we've started. */
if (ipc_sync_signal(IS))
goto die;
/* Clean up. */
if (ipc_sync_done(IS))
goto die;
/* Success! */
return (0);
err1:
ipc_sync_done(IS);
err0:
/* Failure! */
return (-1);
die:
/*
* We're in the child and something bad happened; the parent will be
* notified when we die thanks to the pipe being closed.
*/
_exit(0);
}
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