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From: gordon@sneaky.lonestar.org (Gordon Burditt)
Subject: Re: How to find the filename of the binary executable...
Organization: /usr/lib/news/organi[sz]ation
Message-ID: <D0z930.2rw@sneaky.lonestar.org>
References: <3c35e2$6sv@shore.shore.net>
Date: Sat, 17 Dec 1994 22:57:00 GMT
Lines: 30
>Can someone tell me how to find the filename of the *binary*
>file being executed (on, say, FreeBSD 1.1.5.1, or sunos.recent)?
>
>P.S.: if your answer is argv[0], you don't understand the
>question...
You don't. Especially if there is a security issue involved
(for example, the program is setuid or setgid), and someone has
something to gain by spoofing it.
*THE* filename? Who said there was only one? Who said the
name at the time of the exec() still points at the same file now?
argv[0] might be missing, a convincing lie, or garbage.
The $PATH you inherited might have nothing to do with the $PATH
used to find the executable.
In practice, you can get about 95% of the cases with:
1. If argv[0] begins with a /, use it.
2. If argv[0] contains a /, prepend the current working directory
at the time of the exec() and a /, and use it.
3. Otherwise, try prepending each component of the PATH and a /
to argv[0] in turn, and checking for the existence of a file
with execute permissions. The first one you find, use it.
4. At this point you're down to the other 5%, and you don't have
an answer.
Gordon L. Burditt
sneaky.lonestar.org!gordon