Re: [vox-tech] Identifying the directory that contains the currentlyrunning executable?

[Ken Bloom <kabloom@ucdavMAPSis.edu>]

On Fri, Aug 27, 2004 at 10:30:56AM -0700, Bill Kendrick wrote:
> On Fri, Aug 27, 2004 at 10:28:27AM -0700, Ken Bloom wrote:
> > Is there a way to identify the directory that contains the currently
> > running executable, so that I can programmatically refer to it?
> > i.e. if I am running /usr/bin/myprog, but pwd is /home/bloom, how can
> > I programmatically get either the pathname '/usr/bin' or
> > '/usr/bin/myprog'. (This question asks about a C program).
> 
> Not sure programmatically, but /proc/$PID/exe is a symlink to the 
> program.
> 
> For example, I did "ps aux | grep mysql", found the PID of my
> MySQL client was "4753", and then saw:
> 
>   lrwx------    1 username username      0 Aug 27 10:29 exe -> /usr/bin/mysql
> 
> inside "/proc/4753/"
>
> Does that help at all? :)

I guess that solves the C program problem, because I can use getpid()
to fill in the blank, and readlink(2) to find the elf executable.

That is one wierd symlink. ME wrote in May
(http://www.lugod.org/mailinglists/archives/vox-tech/2004-05/msg00247.html)
about deleting the executable file, then recovering it from
/proc/$PID/exe, so I had assumed it wasn't a symlink. Looking at it
harder, symlinks can't usually point to deleted files [1], but this one
can! You can recover the exe with cat, but not with cp. Really wierd.

Still curious about how to do it with bash scripts.

--Ken Bloom
[1] In the sense that you can use the deleted file through the
symlink. Ordinary symlinks can point at deleted files in a different
sense -- the sense that the symlink is broken.

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