/tmp>cat foo.c
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char ** argv)
{
        pid_t pid;
        int status;

        strcpy(argv[0],"Did you expect this?");

        pid=fork();
        if (pid<0) {
                perror("Can't fork");
        }
        if (pid==0) {
                execlp("ps","ps","-f",NULL);
                exit(127);
        } else {
                waitpid(pid,&status,0);
        }
        exit(0);
}

/tmp>make foo
cc     foo.c   -o foo

/tmp>./foo
UID        PID  PPID  C STIME TTY          TIME CMD
foken     1255  1254  0 15:06 pts/0    00:00:00 -bash
foken     1676  1255  0 15:21 pts/0    00:00:00 Did you expect this?
foken     1677  1676  0 15:21 pts/0    00:00:00 ps -f

/tmp>