Get the name of the caller script in bash script

Question

Let's assume I have 3 shell scripts:

script_1.sh

#!/bin/bash
./script_3.sh

script_2.sh

#!/bin/bash
./script_3.sh

the problem is that in script_3.sh I want to know the name of the caller script.

so that I can respond differently to each caller I support

please don't assume I'm asking about $0 cause $0 will echo script_3 every time no matter who is the caller

here is an example input with expected output

./script_1.sh should echo script_1
./script_2.sh should echo script_2
./script_3.sh should echo user_name or root or anything to distinguish between the 3 cases?

Is that possible? and if possible, how can it be done?

this is going to be added to a rm modified script... so when I call rm it do something and when git or any other CLI tool use rm it is not affected by the modification

Beware modifying the `rm` command (by giving using cover scripts called `rm`, or aliases, or functions). You'll come to rely on the functionality, and then one day you'll find yourself using the raw `rm` command without the protections, and you'll do serious damage because you've been lulled into a false sense of security. — Jonathan Leffler, Dec 13 '13 at 18:27

Thomas Guyot-Sionnest · Accepted Answer · 2018-06-08T04:14:19.270

84

Based on @user3100381's answer, here's a much simpler command to get the same thing which I believe should be fairly portable:

PARENT_COMMAND=$(ps -o comm= $PPID)

Replace comm= with args= to get the full command line (command + arguments). The = alone is used to suppress the headers.

See: http://pubs.opengroup.org/onlinepubs/009604499/utilities/ps.html

edited Jun 08 '18 at 04:14

answered Nov 18 '14 at 03:15

Thomas Guyot-Sionnest

2,251
22
17

10

Cygwin's `ps` does not support the `-o` option. – Koraktor Sep 02 '15 at 11:34
1

If the parent-name is longer than 15 chars, it gets truncated to 15 chars.... (tested on RHEL8). – Rop Aug 27 '22 at 15:30
1

@Rop This is a very standard limitation, the `comm` field is 15 char and generally just the executable name. On multi-threaded processes, it's also common for threads to change their `comm` to help differentiate between threads. The full command being invoked is usually the first argument of `args`, though using `ps` it could be difficult to separate names/paths that could contain a space form the rest of the arguments (on Linux, reading the null-terminated `/proc/self/cmdline` would be a safe way to get the full command and its arguments). – Thomas Guyot-Sionnest Sep 16 '22 at 02:46

Kashyap · Answer 2 · 2023-06-09T17:37:50.750

23

In case you are sourceing instead of calling/executing the script there is no new process forked and thus the solutions with ps won't work reliably.

Use bash built-in caller in that case.

$ cat -n server.sh 
  1  #!/bin/bash
  2  
  3  source common.sh
  4  
  5  [[ $# -ne 2 ]] && warn_me "Error: You messed up"
  6
$ cat -n common.sh 
  1  #!/bin/bash
  2  
  3  function warn_me() {
  4      echo `caller | awk '{print $2":"$1}'` says: "$@"
  5  }
  6
$ ./server.sh 
./server.sh:5 says: Error: You messed up
$

Source

edited Jun 09 '23 at 17:37

answered Mar 13 '15 at 19:43

Kashyap

15,354
13
64
103

@JerryGreen it's a `bash` built-in. What shell are you using? Available at least on GNU bash. – Kashyap Nov 07 '20 at 13:05
I use standard terminal which comes with macos Catalina (10.15.7), it comes with zsh/bash/sh – Jerry Green Nov 07 '20 at 17:01

score 21 · Answer 3 · answered Dec 13 '13 at 18:21

21

The $PPID variable holds the parent process ID. So you could parse the output from ps to get the command.

#!/bin/bash
PARENT_COMMAND=$(ps $PPID | tail -n 1 | awk "{print \$5}")

answered Dec 13 '13 at 18:21

user3100381

464
2
5

Inventive, and probably about as good as you're going to get. Not particularly nice, though. – Jonathan Leffler Dec 13 '13 at 18:26
On some platforms you just need the right options to `ps`, so the tail and Awk (which could easily be refactored to just Awk, btw) can be avoided. – tripleee Dec 13 '13 at 18:32
3

this prints `/bin/bash` – a14m Dec 13 '13 at 18:33
2

@artmees Try it with `awk "{print \$6}"` – Reinstate Monica Please Dec 13 '13 at 19:03
using `$6` make `./script_3` prints `'\n'` empty string and `./script_2` return `'\n./script_3'` – a14m Dec 13 '13 at 19:31
instead could you explain what this `ps $PPID | tail -n 1 | awk "{print \$6}"` should output and i might figure it out – a14m Dec 13 '13 at 19:32
@artmees I think I was looking at a modified ps, $5 is correct. You can just split the commands up to see what they do. First execute `ps $PPID`, then `ps $PPID | tail -n 1` , then add the awk. You could also add the F flag to`ps`to get command arguments, though sed of the file ps reads still feels slightly simpler. – Reinstate Monica Please Dec 13 '13 at 19:48
Found another site that was recommending ps -ocommand= -p $PPID, which then removes the need for a tail command. – Iain Hallam Apr 28 '14 at 16:09

Gilles Quénot · Answer 4 · 2023-01-18T13:36:14.100

6

Based on @J.L.answer, with more in depth explanations, that works for linux :

cat /proc/$PPID/comm

gives you the name of the command of the parent pid

If you prefer the command with all options, then :

cat /proc/$PPID/cmdline

explanations :

$PPID is defined by the shell, it's the pid of the parent processes
in /proc/, you have some dirs with the pid of each process (linux). Then, if you cat /proc/$PPID/comm, you echo the command name of the PID

Check man proc

edited Jan 18 '23 at 13:36

answered Mar 06 '18 at 00:14

Gilles Quénot

173,512
41
224
223

this doesn't run on MacOs – a14m Mar 06 '18 at 09:12
on linux this is the best answer – Scott Stensland Jan 18 '23 at 13:29
It's worth mentioning that `cat /proc//comm` truncates the program's name to the first 15 characters. A least, that's the result I'm getting on the various Linux hosts I'm using. To obtain a program name that exceeds 15 characters, I use `cat /proc//cmdline` with additional steps to (a) strip the leading directory components from the program path string (e.g., basename(1)) and (b) strip command line arguments that follow the program name. – Jim Fischer Jul 26 '23 at 17:27

Reinstate Monica Please · Answer 5 · 2013-12-13T19:31:52.663

2

Couple of useful files things kept in /proc/$PPID here

/proc/*some_process_id*/exe A symlink to the last executed command under *some_process_id*
/proc/*some_process_id*/cmdline A file containing the last executed command under *some_process_id* and null-byte separated arguments

So a slight simplification.

sed 's/\x0/ /g' "/proc/$PPID/cmdline"

edited Dec 13 '13 at 19:31

answered Dec 13 '13 at 19:24

Reinstate Monica Please

11,123
3
27
48

this is not working `sed: /proc/97727/cmdline: No such file or directory` – a14m Dec 13 '13 at 19:34
@artmees What files do you have if you `cd` to /proc/97727? And if you don't have that, do you have any pid directories in /proc? – Reinstate Monica Please Dec 13 '13 at 19:40
i don't have /proc directory – a14m Dec 13 '13 at 20:20
@artmees What platform are you running on? – Reinstate Monica Please Dec 13 '13 at 20:25
mac osx but it needs to run on both osx and linux – a14m Dec 13 '13 at 20:31
@artmees Can't test it at the moment, but try `ps -Af -p $PPID | awk {'print $8'}`. I'm sure there is some location it's stored as well (you might be able to trace it out of ps), but tough to figure out without access to the system and doesn't matter all that much. – Reinstate Monica Please Dec 14 '13 at 01:31
@artmees Actually don't need the A, but do need to cut header. So do `ps -f -p $PPID | tail -n 1 | awk {'print $8'}` – Reinstate Monica Please Dec 14 '13 at 01:41

score 1 · Answer 6 · edited Mar 06 '18 at 00:12

1

If you have /proc:

$(cat /proc/$PPID/comm)

edited Mar 06 '18 at 00:12

Gilles Quénot

173,512
41
224
223

answered Jan 05 '17 at 14:55

J.L.

19
1

Can you explain a bit more? – Dieter Meemken Jan 05 '17 at 15:09
This is a UUOC. You can do a simple `$(< /proc/$PPID/comm)` – lovasoa May 06 '19 at 15:04

score 0 · Answer 7 · edited Aug 26 '20 at 22:00

0

You can simply use the command below to avoid calling cut/awk/sed:

ps --no-headers -o command $PPID

If you only want the parent and none of the subsequent processes, you can use:

ps --no-headers -o command $PPID | cut -d' ' -f1

edited Aug 26 '20 at 22:00

HoldOffHunger

18,769
10
104
133

answered Oct 16 '14 at 14:18

Six

5,122
3
29
38

score 0 · Answer 8 · answered Apr 18 '20 at 12:44

0

Declare this:

PARENT_NAME=`ps -ocomm --no-header $PPID`

Thus you'll get a nice variable $PARENT_NAME that holds the parent's name.

answered Apr 18 '20 at 12:44

Snehasish Sarkar

134
10

score -4 · Answer 9 · answered Dec 13 '13 at 17:59

-4

You could pass in a variable to script_3.sh to determine how to respond...

script_1.sh

#!/bin/bash
./script_3.sh script1

script_2.sh

#!/bin/bash
./script_3.sh script2

script_3.sh

#!/bin/bash
if [ $1 == 'script1' ] ; then
  echo "we were called from script1!"
elsif [ $1 == 'script2' ] ; then
  echo "we were called from script2!"
fi

answered Dec 13 '13 at 17:59

Donovan

15,917
4
22
34

this is not possible as i'm trying add a script that handles special case of `rm` and i want it to be called if i called `rm` not if `git` used `rm` to remove some info. – a14m Dec 13 '13 at 18:00
please clarify your original question then, because that was not clear from your examples. – Donovan Dec 13 '13 at 18:01
I do not think it is possible to obtain the calling program from within a bash script the way you want, I'm sorry. – Donovan Dec 13 '13 at 18:02

Get the name of the caller script in bash script

9 Answers9

explanations :

Check man proc

Linked

Related