signal SIGCHLD

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h> #include <pthread.h> #include <signal.h> #include <sys/types.h> #include <sys/wait.h> #include <unistd.h> int g_count = 0; void display_status(int status) { if (WIFEXITED(status)) printf("normal termination, exit status = %d/n", WEXITSTATUS(status)); else if (WIFSIGNALED(status)) printf("abnormal termination, signal number = %d, %s/n", WTERMSIG(status), #ifdef WCOREDUMP WCOREDUMP(status) ? "(core file generated)" : "" #else "" #endif ); else if (WIFSTOPPED(status)) printf("child stopped, signal number = %d/n", WSTOPSIG(status)); } void sig_handler(int sig) { pid_t pid; int status; assert(SIGCHLD == sig); do { pid = waitpid(-1, &status, WNOHANG); if (0 == pid) { // no more childs printf("waitpid returns %d/n", pid); break; } if (pid < 0) { printf("waitpid returns %d/n", pid); break; } printf("SIGCHLD from process %d/n", pid); display_status(status); g_count++; } while(pid); } void launch_process(int id) { pid_t pid = fork(); switch(pid) { case -1: // error break; case 0: // this is the child { printf("child process %d created by %d/n", getpid(), getppid()); // char *argv[] = {"", "-la", ".", NULL}; // execve("/bin/ls", argv, NULL); if (id == 0) exit(1); else if (id == 1) abort(); else exit(0); } break; default: // this is the father break; } } int main(void) { int rc; int i; struct sigaction action; printf("enter main process %d/n", getpid()); memset(&action, 0, sizeof(action)); action.sa_handler = sig_handler; action.sa_flags = SA_RESTART; rc = sigemptyset(&(action.sa_mask)); rc = sigaddset(&(action.sa_mask), SIGCHLD); rc = sigaction(SIGCHLD, &action, NULL); if (0 != rc) { return -1; } for (i=0; i<3; i++) { launch_process(i); } while (g_count != 3) sleep(1); printf("main process %d exited/n", getpid()); return 0; } 

 

enter main process 2241

child process 2242 created by 2241
SIGCHLD from process 2242
normal termination, exit status = 1
waitpid returns -1

child process 2244 created by 2241
SIGCHLD from process 2244
normal termination, exit status = 0
waitpid returns 0

child process 2243 created by 2241
SIGCHLD from process 2243
abnormal termination, signal number = 6,
waitpid returns -1

main process 2241 exited