Configuration file reading in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a configuration file in scripting?

A configuration file stores settings or options that a script can read to change its behavior without changing the script code.

beginner

How do you read a simple key-value pair from a configuration file in Bash?

You can use the 'source' command to load the file if it contains valid Bash syntax, or use tools like 'grep' and 'cut' to extract values.

beginner

What does the command 'source config.cfg' do in a Bash script?

It runs the commands inside 'config.cfg' in the current shell, making variables and functions defined there available to the script.

intermediate

Why should configuration files avoid complex commands when used with 'source'?

Because 'source' executes the file as code, complex commands can cause errors or unexpected behavior. Configuration files should only set variables.

intermediate

How can you safely read a configuration file with comments and blank lines in Bash?

Use 'grep' to ignore comments and blank lines, then parse key-value pairs with 'cut' or 'awk' to extract needed values.

Which Bash command loads variables from a configuration file into the current script?

A cat

B source

C echo

D grep

The 'source' command runs the file in the current shell, loading variables and functions.

What is the best format for a configuration file to be sourced by a Bash script?

A Plain text with key=value pairs

B Binary file

C JSON format

D XML format

Bash can easily source files with simple key=value pairs as variable assignments.

How can you ignore comment lines starting with '#' when reading a config file with grep?

A grep -i 'comment' config.cfg

B grep '^#' config.cfg

C grep -v '^#' config.cfg

D grep -c '#' config.cfg

The '-v' option inverts match, so lines starting with '#' are excluded.

If a config file has 'PORT=8080', how do you access this value after sourcing it?

A echo PORT

B PORT()

C get PORT

D $PORT

After sourcing, variables are available as shell variables accessed with a '$' prefix.

What happens if a config file sourced by Bash contains commands that delete files?

A Those commands will run and may delete files

B They will be ignored

C An error will occur

D The script will skip those lines

Sourcing runs all commands in the file, so dangerous commands will execute.

Explain how to safely read and use a configuration file in a Bash script.

Think about how the script gets settings without errors.

Describe the risks of sourcing an untrusted configuration file in Bash.

Consider what happens when code runs unexpectedly.