contains the name that was used to invoke the calling program.
This is the same as the value of
with the difference that the scope of
contains the basename component of name that was used to invoke
the calling program.
That is, it is the same value as
with all text up to and including the final slash (/), if any, removed.
These variables are automatically initialized by the glibc run-time
These variables are GNU extensions, and should not be
used in programs intended to be portable.
file provides access to similar information.