Hands-On System Programming with Linux

Summary table – exec family of APIs

Here is a table to summarize all seven of the exec family APIs:

Exec API	Arguments: long format (l)	Arguments: short format (v)	PATH searched? (p)	Environment passed? (e)	API layer
execl	Y	N	N	N	Lib
execlp	Y	N	Y	N	Lib
execle	Y	N	N	Y	Lib
execv	N	Y	N	N	Lib
execvp	N	Y	Y	N	Lib
execvpe	N	Y	Y	Y	Lib
execve	N	Y	N	Y	SysCall

The exec APIs format: exec<foo>, where <foo> is differing combinations of {l,v,p,e}.

All the listed APIs, on success, as we have learned, do not return at all. Only upon failure, would you see a return value; as per the usual norms, the global variable errno will get set to reflect the cause of the error, which can be conveniently looked up via the perror(3) or strerror(3) ...