System Interface Guide

exec(2)

exec is the name of a family of functions that includes execl, execv, execle, execve, execlp, and execvp. All load a new process over the calling process, but with different ways of pulling together and presenting the arguments of the function. For example, execl could be used like this

	execl("/usr/bin/prog2", "prog2", progarg1, progarg2, (char (*)0));

The execl argument list is:

`/usr/bin/prog2`	The path name of the new program file.
`prog2`	The name the new process gets in its `argv[0]`.
`progarg1`, `progarg2`	The arguments to `prog2` as `char (*)`s.
`(char (*)0)`	A null char pointer to mark the end of the arguments.

See execl(2) for more details.

There is no return from a successful execution of any variation of exec(); the new process overlays the process that calls exec. The new process also takes over the process ID and other attributes of the old process. If a call to exec fails, control is returned to the calling program with a return value of -1. You can check errno to learn why it failed.