bash Cookbook

Testing bash Script Syntax

Problem

You are editing a bash script and want to make sure that your syntax is correct.

Solution

Use the -n argument to bash to test syntax often, ideally after every save, and certainly before committing any changes to a revision control system:

$ bash -n my_script
$
$ echo 'echo "Broken line' >> my_script
$ bash -n my_script
my_script: line 4: unexpected EOF while looking for matching `"'
my_script: line 5: syntax error: unexpected end of file

Discussion

The -n option is tricky to find in the bash manpage or other reference material since it’s located under the set built-in. It is noted in passing in bash --help for -D, but it is never explained there. This flag tells bash to “read commands but do not execute them,” which of course will find bash syntax errors.

As with all syntax checkers, this will not catch logic errors or syntax errors in other commands called by the script.

See Also

• man bash

• bash --help

• bash -c “help set”

• bash Startup Options