program_invocation_name, program_invocation_short_name - obtain name used to invoke calling program

#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <errno.h>
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[0] 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.

proc(5)