CODEWITHSUNDEEP
linuxprocesssystem-calls
euphoria83
euphoria83

Reputation: 15136

How do I get the root directory of a process programmatically?

On Linux, every process has its own root directory. For most processes, this is /. However, chroot can change that. This information is exposed via /proc. However, how do I find out the root directory of a process programmatically? Is there a syscall, or, libc function for it?

Upvotes: 1

Views: 2448

Answers (3)

DPlagueis
DPlagueis

Reputation: 67

One simple way is to just use a for loop. This is a one-liner that will print out the root directory of each of the processes you wish (proc1, proc2, proc3):

for i in $(ps -ef | grep -E 'proc1|proc2|proc3' | awk '{ print $2 }'); do ls -ld /proc/$i/root; done

Upvotes: 0

that other guy
that other guy

Reputation: 123600

I don't know whether there is another way, but lots of programs rely on the machine readable files in /proc to get additional information about processes and there's nothing inherently wrong with that.

Here's an example of a process finding its own root dir programmatically via /proc:

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

int main() {
  char foo[PATH_MAX+1];
  int count = readlink("/proc/self/root", foo, PATH_MAX);
  if(count < 0) {
    perror("Can't find root dir (is /proc mounted here?)");
  } else {
    foo[count]=0;
    printf("My root dir is %s\n", foo);
  }
}

Upvotes: 1

Rajnesh
Rajnesh

Reputation: 923

Well there isn't. There exists a command to do this which is pwdx, here is its code https://elixir.bootlin.com/busybox/latest/source/procps/pwdx.c. It also reads root dir from /proc. You can get the pid of your process using getpid function.

Upvotes: 0

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