Can an executable discover its own path? (Linux)

Well, you have to use getcwd() in conjuction with argv[0]. The first one gives you the working directory, the second one gives you the relative location of the binary from the working directory (or an absolute path).

Edit: It was pointed out that using /proc/self/exe is more straightforward. That is entirely true, but I didn't see any benefit in editing the code. Since I still get comments about it, I've edited it.

#include <unistd.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>

int main()
{
  char dest[PATH_MAX];
  memset(dest,0,sizeof(dest)); // readlink does not null terminate!
  if (readlink("/proc/self/exe", dest, PATH_MAX) == -1) {
    perror("readlink");
  } else {
    printf("%s\n", dest);
  }
  return 0;
}

Initial answer: You can use getpid() to find the pid of the current process, then read /proc/<pid>/cmdline (for a human reader) or /proc/<pid>/exe which is a symlink to the actual program. Then, using readlink(), you can find the full path of the program.

Here is an implementation in C:

#include <sys/types.h>
#include <unistd.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>

int main()
{
  char path[PATH_MAX];
  char dest[PATH_MAX];
  memset(dest,0,sizeof(dest)); // readlink does not null terminate!
  pid_t pid = getpid();
  sprintf(path, "/proc/%d/exe", pid);
  if (readlink(path, dest, PATH_MAX) == -1) {
    perror("readlink");
  } else {
    printf("%s\n", dest);
  }
  return 0;
}

If you want to try, you can then compile this, make a symlink from the executable to an other path, and call the link:

$ gcc -o mybin source.c
$ ln -s ./mybin /tmp/otherplace
$ /tmp/otherplace
/home/fser/mybin

Use the proc filesystem

Your flow would be:

• Get pid of executable
• look at /proc/PID/exe for a symlink

The file /proc/self/exe is a simlink to the currently running executable.