Exec system call

The exec() family executes a file as a new process. See fork system call for "cloning" a process.

The

Simple use

The execlp() is one of the function call in the exec family. See manpage

The five arguments in the execlp() below is:

1. ls - the executable file must be in $PATH
2. ls - argv[0] as seen from the executable file
3. -l - argv[1] as seen from the executable file
4. /etc - argv[2] as seen from the executable file
5. NULL - argv[3] as seen from the executable file - end of argument list

#include <stdio.h>
#include <unistd.h>
int main()
{
        execlp("ls", "ls", "-l", "/etc", NULL); // See security note below!!!
        return 1;
}

Security

As execlp() searches through $PATH to find the executable file - it is possible to put an executable with the same name earlier in $PATH and run a bogus and evil program. Use execl("/usr/bin/ls", "ls", "-l", "/etc", NULL); instead if possible.