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I am using OSX on a Mac and use Terminal quite often. I have built a few startup scripts that execute on shell open with the .bash_profile file. However, I would like to be able to have one of them run only on the open of the first shell session when I launch the Terminal app. I can't figure out how to have it launch just once on Terminal app open (the first bash shell opened) but not on subsequently opened new shells.

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Here's how I just did it:

I added this to .bash_profile

# Only do this in the first terminal opened
termsOpen=$(who | grep 'ttys' | wc -l)

if (( $termsOpen < 2 )); then
    echo "This is echoed in the first tty opened only"
fi

So, upon launching the terminal the first time, I get this output:

Last login: Mon Sep 26 08:30:42 on ttys001
This is echoed in the first tty opened only

When I open another terminal (and thus have two terminal windows open at the same time) I get this output:

Last login: Mon Sep 26 08:33:43 on ttys000


How it works:
Every time a new terminal window is opened .bash_profile is sourced. This command

who | grep 'ttys' | wc -l

simply counts the number of terminal windows that are open. If they are lower than 2 (in other words; there is only one terminal window active), then echo This is echoed in the first tty opened only



Version info:

OS X Version: 10.11.5

bash --version
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin15)
  • Good work man, works great. The command I wanted to issue actually as a part of the code closes the window it's currently launched in (it's essentially like f.lux for the command line whereby if it's after a certain hour it launches a night themed command line for working late and regular if it's daytime) so that took a little bit of finagling with this solution but I just put a sleep in so that after it opened the second terminal, the first stayed open long enough that the conditional didn't trigger and then it exits the first terminal. – MLP Sep 28 '16 at 2:51
  • @MLP I am glad that you were able to implement it! – maulinglawns Sep 28 '16 at 5:42

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