Changing the current working directory of a certain process

cwdprocess

Can I change the current working directory of a certain process?

For example, I am running a process that has the pid 1000. Right now, its current working directory is ~. I want to change its current working directory to ~/1. How can I do it?

Best Answer

You can use the following script (found here)

#!/bin/bash

pid="$1" # first arguvment is the PID
cwd="$2" # second argument is the target working directory

# now let's command the GNU debugger
gdb -q <<EOF
  attach $pid
  call (int) chdir("$cwd")
  detach
  quit
EOF

Call it by passing the PID as the first parameter and the target working directory as the second.

Caveats: This may have unexpected consequences on the target process, including files being closed, and misleading information provided in shell prompts for example.

You also need gdb installed (obviously).

Related Solutions

Shell – What’s the best way to determine the working directory for UNIX process using ‘ps’

I'm not sure if that answers your question, but the pwdx could give you the current working directory of any process.

Like this:

pwdx <PID>

You could also do what Ulrich Schwarz said and run

ls -l /proc/PID/cwd

Process Management – What Does It Mean Each Process Has a Current Directory?

Conceptual level

When you start a process from your shell, the current working directory of the process is the same as the current working directory of your shell. In the context of the shell, the current working directory is the location you are currently "at."

The current working directory of any process is used to interpret relative paths. For example, if your shell's current working directory was /home/rene and you ran ls .. from the shell, the process's current working directory, /home/rene, would be used to resolve .. to /home.

You can see the current working directories of all of the processes running on your system with lsof | grep '\scwd\s' (note that you'll probably need to be root to see other users' processes.) This can give you an idea of how current working directories relate to the processes running on your system.

Program level

The current working directory of the shell is the directory you see and modify with the shell built-ins pwd and cd respectively. These commands call system calls such as getcwd and chdir that work with the current working directory of your shell.

Using bash as an example, the cd built-in eventually runs this line:

if (chdir (nolinks ? newdir : tdir) == 0)

and the pwd built-in eventually runs this line:

the_current_working_directory = getcwd (0, PATH_MAX);

The shell is just a convenient example of the current working directory's use; these same system calls are used by other programs as well. A program can change its current working directory to /usr and any relative paths that the program uses will start from the /usr directory,

Kernel level

The current working directory of a process is stored by the kernel. Linux stores it in the pwd member of a fs_struct pointed to by the fs member of a task_struct. The pwd member is a path struct, which points to information about the mount (vfsmount) and the directory's location in the filesystem (dentry). Each process has a task_struct associated with it.

The chdir and getcwd system calls modify and retrieve information in pwd.

Best Answer

Related Solutions

Shell – What’s the best way to determine the working directory for UNIX process using ‘ps’

Process Management – What Does It Mean Each Process Has a Current Directory?

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