Debug a script

From Linux Shell Scripting Tutorial - A Beginner's handbook
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You need to run a shell script with -x option from the command line itself:

bash -x script-name

OR

bash -xv script-name

You can also modify shebang line to run an entire script in debugging mode:

#!/bin/bash -x
echo "Hello ${LOGNAME}"
echo "Today is $(date)"
echo "Users currently on the machine, and their processes:"
w

Use of set builtin command

Bash shell offers debugging options which can be turn on or off using set command.

  • set -x : Display commands and their arguments as they are executed.
  • set -v : Display shell input lines as they are read.
#!/bin/bash
### Turn on debug mode ###
set -x

# Run shell commands
echo "Hello ${LOGNAME}"
echo "Today is $(date)"
echo "Users currently on the machine, and their processes:"
w

### Turn OFF debug mode ###
set +x

# Add more commands without debug mode