Add Gracefully Exit A Script With Trap as a Unix TIL

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1507 TILs and counting..._
+_1508 TILs and counting..._
 
 ---
 
@@ -1465,6 +1465,7 @@ _1507 TILs and counting..._
 - [Global Substitution On The Previous Command](unix/global-substitution-on-the-previous-command.md)
 - [Globbing For All Directories In Zsh](unix/globbing-for-all-directories-in-zsh.md)
 - [Globbing For Filenames In Zsh](unix/globbing-for-filenames-in-zsh.md)
+- [Gracefully Exit A Script With Trap](unix/gracefully-exit-a-script-with-trap.md)
 - [Grep For Files Without A Match](unix/grep-for-files-without-a-match.md)
 - [Grep For Files With Multiple Matches](unix/grep-for-files-with-multiple-matches.md)
 - [Grep For Multiple Patterns](unix/grep-for-multiple-patterns.md)

unix/gracefully-exit-a-script-with-trap.md

@@ -0,0 +1,29 @@
+# Gracefully Exit A Script With Trap
+
+With `trap` you can intercept signals that would cause your script to exit and
+then inject some additional behavior. Perhaps you want to make sure the script
+cleans up after itself before it exists.
+
+During this script's execution, it creates a file in the filesystem. It would
+be nice to make sure that no matter path this script ends up down that it will
+clean up after itself as it exits. We set up a `trap` that looks for the `EXIT`
+signal to do this.
+
+```bash
+# Set up trap
+trap 'echo "Cleaning up temp files"; rm -f *.tmp' EXIT
+
+# Create temporary file
+echo "test data" > work.tmp
+
+# Do some work
+cat work.tmp
+
+# Trap will clean up on exit
+```
+
+Whatever is in quotes is what the trap will execute when it is triggered. The
+following one or more signals are what the trap listens for, in this case
+`EXIT`.
+
+[source](https://tldp.org/LDP/Bash-Beginners-Guide/html/sect_12_02.html)