How do I find the location of the executable in C? [duplicate]

Answer 1

In many POSIX systems you could check a simlink located under /proc/PID/exe. Few examples:

# file /proc/*/exe
/proc/1001/exe: symbolic link to /usr/bin/distccd
/proc/1023/exe: symbolic link to /usr/sbin/sendmail.sendmail
/proc/1043/exe: symbolic link to /usr/sbin/crond

Answer 2

Remember that on Unix systems the binary may have been removed since it was started. It's perfectly legal and safe on Unix. Last I checked Windows will not allow you to remove a running binary.

/proc/self/exe will still be readable, but it will not be a working symlink really. It will be... odd.

Answer 3

To summarize:

• On Unixes with /proc really straight and realiable way is to:

  • readlink("/proc/self/exe", buf, bufsize) (Linux)

  • readlink("/proc/curproc/file", buf, bufsize) (FreeBSD)

  • readlink("/proc/self/path/a.out", buf, bufsize) (Solaris)

• On Unixes without /proc (i.e. if above fails):

  • If argv[0] starts with "/" (absolute path) this is the path.

  • Otherwise if argv[0] contains "/" (relative path) append it to cwd (assuming it hasn't been changed yet).

  • Otherwise search directories in $PATH for executable argv[0].

  Afterwards it may be reasonable to check whether the executable isn't actually a symlink. If it is resolve it relative to the symlink directory.

  This step is not necessary in /proc method (at least for Linux). There the proc symlink points directly to executable.

  Note that it is up to the calling process to set argv[0] correctly. It is right most of the times however there are occasions when the calling process cannot be trusted (ex. setuid executable).

• On Windows: use GetModuleFileName(NULL, buf, bufsize)