mjhjmtu

I have a Bash script I was trying to make to help me run a rather complex command with small changes that it would ask me about through echo and read.

I have found solutions to force it to run a terminal to execute the command, but I'm not interested in that. What I would like it to do is, if I space out and just hit Enter on it in Nautilus (making it run with Run Software), it'll just gently pop up a notification saying "Please run this from a terminal."

I can get the popup to happen -- as in I know the command -- but I can't get the Bash script to tell if it's being run inside a terminal or not, it seems to always think so. Is it even possible?

From man bash under CONDITIONAL EXPRESSIONS:

-t fd 
 True if file descriptor fd is open and refers to a terminal.

Assuming fd 1 is standard out, if [ -t 1 ]; then should work for you. The Advanced Shell Scripting Guide claims that -t used this way will fail over ssh, and that the test (using stdin, not stdout) should therefore be:

if [[ -t 0 || -p /dev/stdin ]]

-p tests if a file exists and is a named pipe. However, I'd note experientially this is not true for me: -p /dev/stdin fails for both normal terminals and ssh sessions whereas if [ -t 0 ] (or -t 1) works in both cases (see also Gilles comments below about issues in that section of the Advanced Shell Scripting Guide).

If the primary issue is a specialized context from which you wish to call the script to behave in a way appropriate to that context, you can sidestep all these technicalities and save your self some fuss by using a wrapper and a custom variable:

!#/bin/bash

export SPECIAL_CONTEXT=1
/path/to/real/script.sh

Call this live_script.sh or whatever and double click that instead. You could of course accomplish the same thing with command line arguments, but a wrapper would still be needed to make point and click in a GUI file browser work.

Use the bash $SHLVL variable to detect the level of shell nesting.
In a script run 'raw' by double-clicking it will be 1, in a script running within a terminal it will be 2.

#!/bin/bash
if (( SHLVL < 2 )) ; then
 echo "Please run this from a terminal."
 read -p "Press <Enter> to close this window"
 exit 1
fi
# rest of script

Another, using the bash options set internal variable, $-.

From .bashrc,

# If not running interactively, don't do anything
case $- in
 *i*) ;;
 *) return;;
esac