1. Overview
In this tutorial, we’ll discuss how to find the path of a process in Linux. As we know, each process has a unique PID. We can use that PID to get the path of any process.
2. Finding the PID
We can get the PID of a process with the help of the ps command.
Let’s start an editor process and get its PID using the ps command:
$ gedit test.c
$ ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
... ... ... ... ... ... ... ... ... ... ...
HARDIK 10899 2.3 1.3 797076 42716 pts/1 Sl 01:49 0:00 gedit test.c
... ... ... ... ... ... ... ... ... ... ...Here, the ps command with option a lists all the processes for all users. We can see the user of the process by adding an option u. Moreover, option x will include processes without a controlling terminal. However, issuing this command may print lots of lines of data regarding processes.
Thus, from the above output, we can see that the PID of our newly created process is 10899. We will use this PID to get the desired information.
Moreover, we can use the ps command in combination with the grep command to list our process using its name:
$ ps aux | grep gedit
HARDIK 10899 2.3 1.3 797076 42716 pts/1 Sl 01:49 0:00 gedit test.c3. Finding the Process Path
3.1. proc File System and exe Symbolic Link
Information about processes is stored under the /proc directory, also called the proc filesystem. In this directory, each process stores its data in a sub-directory named after its PID.
If we list the directories in our proc file system, we see lots of directories named as numbers. These are nothing but PIDs of processes:
$ ls /proc
1 11772 1400 174 199 219 245 283 320 359 397 46 650 85 interrupts
10 11773 141 175 1991 22 246 284 321 36 398 47 651 86 iomem
100 11780 142 1754 2 220 247 285 322 360 399 48 652 87 ioports
101 118 143 1755 20 221 248 286 323 361 40 486 653 878 irq
102 119 144 1756 200 222 249 287 324 362 400 49 654 879 kallsyms
... ... ... ... ... ... ... ... ... ... ... ... ... ... ...Furthermore, if we list the content of the directory named after the PID of the process we created earlier, we can see a few directories and symbolic links:
$ ls -a /proc/10899/
. clear_refs environ latency mountinfo oom_adj root stat uid_map
.. cmdline exe limits mounts oom_score sched statm wchan
attr comm fd loginuid mountstats oom_score_adj schedstat status
autogroup coredump_filter fdinfo map_files net pagemap sessionid syscall
auxv cpuset gid_map maps ns personality smaps task
cgroup cwd io mem numa_maps projid_map stack timersA symbolic link is a file that contains a text string in the form of a path that references another file or directory. Among these, the symbolic link exe contains the actual pathname of the executed command. We can get the path of our process by reading this symbolic link.
Next, we will see different ways to get the path of the process using its PID and symbolic link.
3.2. Using readlink Command and exe Symbolic Link
The readlink command displays the value of resolved symbolic links or canonical file names.
Here, when we read the exe symbolic link, it returns the path of the gedit executable:
$ readlink /proc/10899/exe
/usr/bin/geditTherefore, from the above output, it’s clear that the editor has been executed from the /usr/bin/ directory.
Additionally, we can use the verbose option(v) to list error messages, if any. For example, if we have entered the wrong PID, which does not exist, it displays an error message:
$ readlink -v /proc/10890/exe
readlink: /proc/10890/exe: No such file or directory3.3. Using realpath Command and exe Symbolic Link
Alternatively, we can use the realpath command. This command prints the resolved path for the given symbolic link:
$ realpath /proc/10899/exe
/usr/bin/gedit3.4. Using ls Command and exe Symbolic Link
We can also use the ls command, which lists the directory content. By using ls in combination with the long listing option (l), we can know the path of the process:
$ ls -l /proc/10899/exe
lrwxrwxrwx 1 HARDIK users 0 Feb 23 01:49 /proc/10899/exe -> /usr/bin/gedit4. Conclusion
In this article, we discussed how to get the path of a process from its PID in Linux. We saw that using the ps command we can get the PID of the process, and the exe symbol link of that PID gives us the path of that process.