Debugging shell scripts is an important part of the development process as it helps you identify and correct errors in your scripts. There are several techniques that can be used to debug shell scripts, including displaying variables and logging errors.
Variable display
You can use the “echo” command to display the value of a variable at a certain point in your script. For example:
#!/bin/bash
name=”John”
echo “The name is $name”
When running this script, the output will be “The name is John”. This can help verify that variables are being assigned correctly.
Error logging
You can use the “set -e” command at the beginning of your script to automatically terminate the script if an error occurs. Additionally, you can use the “set -x” command to enable debug mode, which displays each command as it is executed. For example:
#!/bin/bash
set -e
set -x
echo “Starting script”
ls /nonexistent_dir
echo “End of script”
When running this script, you will get an error message that the directory does not exist and the script will exit. In addition, debug mode will display each command executed, making it easier to identify where the error occurred.
Output redirection
You can redirect the output of your script to a log file, which can be useful for analyzing errors later. For example:
#!/bin/bash
exec &> log.txt
echo “Starting script”
ls /nonexistent_dir
echo “End of script”
When running this script, the output will be redirected to the “log.txt” file. If an error occurs, it will be logged to this file.