program_invocation_name, program_invocation_short_name - obtain name used to invoke calling program
#define _GNU_SOURCE /* See feature_test_macros(7) */
extern char *program_invocation_name;
extern char *program_invocation_short_name;
program_invocation_name contains the name that was used to invoke the calling program. This is the same as the value of argv in main(), with the difference that the scope of program_invocation_name is global.
program_invocation_short_name contains the basename component of name that was used to invoke the calling program. That is, it is the same value as program_invocation_name, with all text up to and including the final slash (/), if any, removed.
These variables are automatically initialized by the glibc run-time startup code.
These variables are GNU extensions, and should not be used in programs intended to be portable.
The Linux-specific /proc/[number]/cmdline file provides access to similar information.