Bash Trap Command

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Overview

Sources:

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Code Snippet

#!/bin/bash
 
# traptest.sh
# notice you cannot make Ctrl-C work in this shell, 
# try with your local one, also remeber to chmod +x 
# your local .sh file so you can execute it!
 
trap "echo Booh!" SIGINT SIGTERM
echo "it's going to run until you hit Ctrl+Z"
echo "hit Ctrl+C to be blown away!"
 
while true        
do
    sleep 60       
done

You can substitute the "echo Booh!" trap with a function:

function booh {
  echo "booh!"
}

then:

trap booh SIGINT SIGTERM

Some of the common signal types you can trap:

• SIGINT: user sends an interrupt signal (Ctrl+C)
• SIGQUIT: user sends a quit signal (Ctrl+D)
• SIGFPE: attempted an illegal mathematical operation

You can check out all signal types by entering the following command:

kill -l

Notice the numbers before each signal name, you can use that number to avoid typing long strings in trap:

#2 corresponds to SIGINT and 15 corresponds to SIGTERM
trap booh 2 15

one of the common usage of trap is to do cleanup temporary files:

trap "rm -f folder; exit" 2

Details

About

This note is about the trap command in a Linux Shell, or Bash.

It often comes the situations that you want to catch a special signal/interruption/user input in your script to prevent unpredictable events.

Trap is the command for this use-case: trap <arg/function> <signal>.

See Also

• Bash Code Snippets
• Linux, Ubuntu, Kali Linux
• Zsh
• Development Map of Content
• Windows Sub-System for Linux (WSL)

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Appendix

Note created on 2024-04-15 and last modified on 2024-04-15.

Backlinks

LIST FROM [[Bash - Trap Command]] AND -"CHANGELOG" AND -"04-RESOURCES/Code/Bash/Bash - Trap Command"

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