How do I handle Sigchld?

status = 0; 
 pid_t child, endID;
 if(amp == 1)
 signal( SIGCHLD, SIG_IGN ); 
< br /> child = fork(); 

 if (child <0) {
 perror("fork() error
");
 exit(EXIT_FAILURE);< br />
} else if (child == 0) {
 // do sth here
 perror("error
");

} else { 
 //sleep(1)

static void
child_handler(int sig)
{
 pid_t pid;
 int status;

 /* EEEEXTEERMINAAATE! */
 while((pid = waitpid(-1, &status, WNOHANG))> 0)
 ;
}

/* Establish handler. */< br />struct sigaction sa;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_handler = child_handler;

sigaction(SIGCHLD, &sa, NULL);

signal(SIGCHLD, SIG_IGN); /* Silently (and portably) reap children. */

I need to handle SIGCHL correctly D. How to use it in existing code. Currently I cannot wait for the child process unless I use 0 instead of WNOHANG | WUNTRACED.

status = 0; < br /> pid_t child, endID;
 if(amp == 1)
 signal( SIGCHLD, SIG_IGN ); 

 child = fork(); 

 if (child <0) {
 perror("fork() error
");
 exit(EXIT_FAILURE);

} else if (child == 0 ) {
 // do sth here
 perror("error
");

} else {
 //sleep(1)

< p>If I delete the sleep then the father is executed first…why?

This is the beginning (but read below):

static void
child_handler(int sig)
{
 pid_t pid;
 int status;

 /* EEEEXTEERMINAAATE! */
 while((pid = waitpid (-1, &status, WNOHANG))> 0)
 ;
}

/* Establish handler. */
struct sigaction sa;
sigemptyset (&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_handler = child_handler;

sigaction(SIGCHLD, &sa, NULL);

Of course, this is meaningless. If parents just ignore SIGCHLD, children will harvest silently and will not become zombies.

Quoting TLPI:

< /p>

Explicitly setting the disposition of SIGCHLD to SIG_IGN causes any
child process that subsequently terminates to be immediately removed
from the system instead of being converted into a zombie.

So something like this should do the trick for you:

signal(SIGCHLD, SIG_IGN); /* Silently ( and portably) reap children. */