Can a fish script distinguish between being sourced and executed?

Question

I have a fish script that exports some variables and launches a command at the end. I'd like to be able to source this file to bring these variables into the current shell session, but without executing the command at the end.

The question: Can I figure out whether the current file is being executed or sourced from within the file?

score 2 · Answer 1 · answered Dec 25 '23 at 00:25

2

You can use the $_ environment variable to see if your script is being "run" by the source command. Note that the source command has a common alias ("."), so you must check the $_ environment variable against both source and ..

#!/bin/fish
if test "$" != "source" -a "$" != "."
    echo "not sourced"
else
    echo "was sourced"
end

A common use of this may be to give a warning to the user, iff the script was not sourced:

if test "$_" != "source" -a "$_" != "."
    echo "Run this script with \". ./activate.fish\" (aka: \"source ./activate.fish\")."
    exit 1
end

Replace activate.fish with the name of your script, of course.

answered Dec 25 '23 at 00:25

HumpbackWhale194

21

How does this differ from the accepted answer that was posted 8+ years ago? – Giacomo1968 Dec 25 '23 at 00:43
It adds the . case (where . is an alias for source). It also adds a common use case of this check, which I wish was included in software like Python's venv activator (instead of just doing nothing silently and leaving you confused). – HumpbackWhale194 Dec 25 '23 at 06:06
Okay. Fair enough. – Giacomo1968 Dec 25 '23 at 06:11

score 2 · Accepted Answer · answered Jul 22 '15 at 06:43

2

You can use the $_ environment variable to see if your script is being "run" by the source command:

#!/bin/fish
if test "$_" = source
  echo got sourced
else
  echo was execed
end

answered Jul 22 '15 at 06:43

meuh

6,309

score 1 · Answer 3 · answered Jul 21 '15 at 18:50

1

I think you misunderstand what "source"ing a script does. Generally, executing a script will run it in a separate process. Sourcing it will execute it in the current shell. It will still execute each line.

Probably what you want to do is to filter out the last line. Try:

source (sed '$d' filename | psub)

The psub command is used to handle the output of some process as if it is a file. Documentation

answered Jul 21 '15 at 18:50

glenn jackman

26,306

That works, and is pretty interesting. What I was thinking about was something akin to the if __name__ == __main__ trick from python, but this works just as well. – mkaito Jul 22 '15 at 01:50

Can a fish script distinguish between being sourced and executed?

3 Answers3