Configuration file reading in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Reading a simple config file with key-value pairs

Given a config file settings.conf with the content:

username=admin
password=secret
port=8080

What is the output of this script?

while IFS='=' read -r key value; do
  echo "$key -> $value"
done < settings.conf

Bash Scripting

while IFS='=' read -r key value; do
  echo "$key -> $value"
done < settings.conf

A

username -> admin
password -> secret
port -> 8080

B

username
admin
password
secret
port
8080

C

username=admin
password=secret
port=8080

D SyntaxError: invalid syntax

💡 Hint

Think about how the read command splits lines using the IFS variable.

The script reads each line splitting at '=' into key and value, then prints them with an arrow.

💻 Command Output

intermediate

Ignoring comments and blank lines in config file

Consider a config file app.conf with:

# This is a comment
host=localhost

# Another comment
port=3306

What does this script output?

grep -v '^#' app.conf | grep -v '^$' | while IFS='=' read -r key value; do
  echo "$key=$value"
done

Bash Scripting

grep -v '^#' app.conf | grep -v '^$' | while IFS='=' read -r key value; do
  echo "$key=$value"
done

A

host=localhost
port=3306

B

# This is a comment
host=localhost

# Another comment
port=3306

C

host
localhost
port
3306

D Error: command not found

💡 Hint

grep -v '^#' removes comment lines, grep -v '^$' removes blank lines.

The script filters out comments and blank lines, then reads key-value pairs and prints them.

📝 Syntax

advanced

Parsing config with spaces around equals sign

Which script correctly reads a config file where lines may have spaces around '=' like:

user = admin
password = secret

and prints key and value?

A while IFS='=' read key value; do echo "$key -> $value"; done < config.txt

B while IFS='=' read -r key value; do echo "$key -> $value"; done < config.txt

C while IFS=' = ' read -r key value; do echo "$key -> $value"; done < config.txt

D while read -r line; do key=${line%%=*}; value=${line#*=}; echo "$key -> $value"; done < config.txt

💡 Hint

Think about how to trim spaces around keys and values.

Option D uses string manipulation to split at '=' and preserves spaces to trim later if needed.

🔧 Debug

advanced

Why does this config reading script fail?

This script tries to read config.cfg and print keys and values:

while IFS='=' read -r key value
 do
  echo "$key: $value"
done < config.cfg

But it prints nothing. What is the problem?

Bash Scripting

while IFS='=' read -r key value
 do
  echo "$key: $value"
done < config.cfg

A File config.cfg is empty

B Missing semicolon or newline after read command causes syntax error

C IFS should be set to ':=' instead of '='

D read command needs -a option to read arrays

💡 Hint

Check the syntax of the while loop and read command carefully.

The read command line must end with a semicolon or newline before 'do'. Without it, the shell does not parse the loop correctly.

🚀 Application

expert

Extracting config values into variables

Given a config file settings.ini with:

host=127.0.0.1
port=8080
user=guest

Which script correctly reads these values and sets bash variables host, port, and user accordingly?

A while IFS='=' read -r key value; do declare "$key=$value"; done < settings.ini

B source settings.ini

C while IFS='=' read -r key value; do export $key=$value; done < settings.ini

D eval $(sed 's/^/export /' settings.ini)

💡 Hint

Think about how to safely assign variables from a file in bash.

Option C reads each line, splits key and value, and exports them as variables. Option C fails because the file is not a valid bash script (no spaces allowed). Option C declares variables but does not export them. Option C uses eval which can be unsafe.