getppid() — Get the parent process ID

Standards

Standards / Extensions C or C++ Dependencies
POSIX.1
XPG4
XPG4.2
Single UNIX Specification, Version 3
 both  

Format

#define _POSIX_SOURCE
#include <unistd.h>

pid_t getppid(void);

General description

Gets the parent process ID (PPID).

Returned value

getppid() returns the parent process ID. It is always successful.

There are no documented errno values.

Example

CELEBG15 
/* CELEBG15 */
#define _POSIX_SOURCE
#include <stdio.h>
#include <sys/types.h>
#include <signal.h>
#include <unistd.h>
#include <sys/wait.h>                  /*FIX: used to be <wait.h>*/

volatile short footprint=0;

void catcher(int signum) {
  switch (signum) {
    case SIGALRM: puts("caught SIGALRM");
                  break;
    case SIGUSR2: puts("caught SIGUSR2");
                  break;
    default: printf("caught unexpected signal %d\n", signum);
  }
  footprint++;
}

main() {
  struct sigaction sact;
  int status;

  sigemptyset(&sact.sa_mask);
  sact.sa_flags = 0;
  sact.sa_handler = catcher;
  sigaction(SIGUSR2, &sact, NULL);

  sigemptyset(&sact.sa_mask);
  sact.sa_flags = 0;
  sact.sa_handler = catcher;
  sigaction(SIGALRM, &sact, NULL);

  printf("parent (pid %d) is about to fork child\n", (int) getpid());

  if (fork() == 0) {
    printf("child is sending SIGUSR2 to pid %d\n", (int) getppid());
    kill(getppid(), SIGUSR2);
    exit(0);
  }

  alarm(30);
  while (footprint == 0);
  wait(&status);
  puts("parent is exiting");
}
Output 
parent (pid 6094854) is about to fork child
is sending SIGUSR2 to pid 6094854
caught SIGUSR2
parent is exiting

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