Debugging Zsh Scripts on macOS Tahoe
Writing scripts is only half the battle; ensuring they run correctly is the other. This guide covers techniques for debugging Zsh scripts on macOS Tahoe. It assumes you are familiar with the basics covered in Scripting with Zsh on macOS Tahoe.
Syntax Checking
Before running a script, you can check it for syntax errors without actually executing the commands.
zsh -n myscript.shIf there is no output, the syntax is likely correct. If there is an error, Zsh will point to the line number.
Execution Tracing
The most common way to debug a script is to see exactly what commands are being executed.
Tracing the Entire Script
You can run the script with the -x (xtrace) flag:
zsh -x myscript.shOr add set -x to the top of your script after the shebang:
#!/bin/zsh
set -x
echo "This command will be printed before execution"This prints every command and its arguments to the terminal as they are executed, usually prefixed with a +.
Tracing Specific Sections
If you only need to debug a specific part of a long script, you can toggle tracing on and off:
#!/bin/zsh
echo "Normal execution..."
set -x
# Debugging starts here
VAR="test"
if <a href='/%20%22%24VAR%22%20%3D%3D%20%22test%22%20'> "$VAR" == "test" </a>; then
echo "Variable matches"
fi
set +x
echo "Back to normal execution..."Verbose Mode
To print the shell input lines as they are read, use the -v (verbose) option. This is useful for finding where a script might be crashing if it's not outputting anything.
zsh -v myscript.shStrict Error Handling
By default, Zsh continues executing a script even if a command fails. To make the script exit immediately upon encountering an error, use set -e.
#!/bin/zsh
set -e
mkdir /root/protected_folder # This will fail
echo "This line will not run because the previous command failed."Unbound Variables
Typos in variable names can lead to silent failures. Use set -u to treat unset variables as an error.
#!/bin/zsh
set -u
NAME="Tahoe"
echo "Welcome to $NMAE" # Typo: This will cause the script to exit with an error