Change behavior of bash script if executed from another script

Question

I have a script (say Task.sh) (with executable permission):

Pseducode:

if [[ Not called from inside a script ]]; then echo 'Not called from inside a script' else echo 'Called from a script' fi 

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I have a script say Main.sh (with executable permission):

Value=$(Task.sh) echo "${Value}" 

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Expected Outcome

$ Task.sh Not called from inside a script $ Main.sh Called from a script 

Help Request

Please suggest what conditional to put in the pseducode for Task.sh

Answer 1

One option is to change the requirements slightly from "am I running in a script?" to "am I connected to a terminal or a pipe/file?". This would allow for the case of Task.sh >/tmp/file: it's not called from a script, but it seems it should write to the file rather than the clipboard.

If that's acceptable then you can use a simple test for stdout connected to a terminal:

if [ -t 1 ] then echo "stdout is a terminal (tty)" else echo "not a terminal (tty)" fi 

Tools like ls and tty operate differently depending on their usage situation using a very similar approach. For example, in a directory with several entries contrast ls and ls | cat

Answer 2

Having a tool copy something to clipboard seems rare enough that it might be better to be explicit about it and only do it when asked.

So one option is to the script check for a command line argument asking to use the clipboard, and otherwise default to printing to stdout.

If you don't use command line arguments in the script otherwise, it's as easy as:

if [ "$1" = --clipboard ]; then copy_to_clipboard "$data" # or whatever else printf "%s\n" "$data" # print to stdout fi 

or include it in your getopt(s) loop if you are using command line arguments.

That means an interactive user will need to remember to add the option, but they can just install an alias in their .bashrc or equivalent to do that:

alias Task.sh="Task.sh --clipboard"