CODEWITHSUNDEEP
cunix
Tomer
Tomer

Reputation: 2448

Trying to find what is the max number of processes I can open

I am a total beginner in C. I have this assginment to wirte a program that will find the max number of processes I can open.

I come out with this code:

int main() {

while (1){
    pid_t pid = fork();
    if(pid) {
        if ( pid == -1){
            fprintf(stderr,"Can't fork,error %d\n",errno);
            exit(EXIT_FAILURE);
        }else{
            int status;
            alarm(30);
            if(waitpid(pid, &status, 0)==pid) {
                alarm(0);
                // the child process complete within 30 seconds
                printf("Waiting.");
            }else {
                alarm(0);
                // the child process does not complete within 30 seconds
                printf("killed");
                kill(pid, SIGTERM);
            }
        }
    }
    else{
        alarm(30);
        printf("child");
    }
}
}

The thing is this program caused my laptop to crash..:-|

I assumed that when the program will not be able to open more processes I will get -1 from the fork() and then will exit the program. Well, it didn't happened.

Any idea? What am I missing here?

Thanks!

Upvotes: 1

Views: 1394

Answers (2)

Frozen Crayon
Frozen Crayon

Reputation: 5400

U cannot "open" a process. You can create them.

CHILD_MAX is a constant that contains the value of max number of child processes that can be created. It is defined in unistd.h header. To query, use the sysconf function. Pass CHILD_MAX argument to sysconf with _SC_ prefix.

#include <stdio.h>
#include <unistd.h>

int main(){
     int res = sysconf(_SC_CHILD_MAX);
     if (res == -1) {
        perror("sysconf");
     } else {
        printf("The max number of processes that can be created is: %d\n", res);
     }

     return 0;
}

Upvotes: 1

Joe
Joe

Reputation: 7798

If you actually want to know how many processes you can open you could use the sysconf call, looking for the _SC_CHILD_MAX variable. Check here.

Upvotes: 2

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