Question

I trying a program with fork and execlp where parent address space is replaced with “ls” command.

#include<stdio.h>
main()
{
    int pid,j=10,fd;
    pid=fork();
    if(pid==0)
    {
        printf("\nI am the child\n");
        execlp("/bin/ls","ls",NULL);
        printf("\nStill I am the child\n");

    }
    else if (pid > 0)
    {
        printf("\n I am the parent\n");
        wait();
    } 
}

When I execute the program the last line of child

printf("\nStill I am the child\n");

is not printed. Why?

Answer 1

exec family functions do not return when successful.

http://pubs.opengroup.org/onlinepubs/009604499/functions/exec.html

The exec family of functions shall replace the current process image with a new process image. The new image shall be constructed from a regular, executable file called the new process image file. There shall be no return from a successful exec, because the calling process image is overlaid by the new process image.

If one of the exec functions returns to the calling process image, an error has occurred; the return value shall be -1, and errno shall be set to indicate the error.