Exit codes ($?) in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the exit code after a successful command?

Consider the following Bash commands run in sequence:

echo "Hello World"
echo $?

What will be the output of the second echo command?

Bash Scripting

echo "Hello World"
echo $?

A 1

B 0

C Hello World

D Command not found

💡 Hint

The exit code $? shows if the last command succeeded or failed. Zero means success.

The first echo command runs successfully and prints "Hello World". The exit code $? after a successful command is 0.

💻 Command Output

intermediate

Exit code after a failing command

What will be the output of this script?

ls /nonexistent_directory
echo $?

Bash Scripting

ls /nonexistent_directory
echo $?

A No such file or directory

B 1

C 2

D 0

💡 Hint

When a command fails, the exit code is non-zero. Different commands may use different codes.

The ls command fails because the directory does not exist. On many systems, ls returns exit code 2 for this error.

📝 Syntax

advanced

Which script correctly checks the exit code?

You want to run a command and then check if it succeeded using its exit code. Which script snippet correctly does this?

A

command
if $? == 0 then
 echo "Success"
fi

B

command
if [ $? -eq 0 ] then
 echo "Success"
fi

C

command
if [$? -eq 0]; then
 echo "Success"
fi

D

command
if [ $? -eq 0 ]; then
echo "Success"
fi

💡 Hint

Remember to have spaces around brackets and use correct syntax for if statements in Bash.

Option D uses correct syntax: spaces around [ and ], the -eq operator, and the then keyword on the same line or next line.

🚀 Application

advanced

What is the exit code after a pipeline?

Consider this pipeline:

grep 'pattern' file.txt | sort
echo $?

What does the exit code represent?

Bash Scripting

grep 'pattern' file.txt | sort
echo $?

A Exit code of the last command in the pipeline (sort)

B Exit code of the first command in the pipeline (grep)

C 0 if both commands succeed, else non-zero

D Sum of exit codes of both commands

💡 Hint

In Bash, $? after a pipeline returns the exit code of the last command by default.

By default, $? returns the exit code of the last command in the pipeline, which is sort here.

🧠 Conceptual

expert

How to get exit codes of all commands in a pipeline?

You run a pipeline of commands in Bash:

cmd1 | cmd2 | cmd3

How can you get the exit codes of all three commands?

A Use the array ${PIPESTATUS[@]} immediately after the pipeline

B Use the command 'exitcodes' after the pipeline

C Use $? three times, once after each command

D Use 'echo $PIPESTATUS' after the pipeline

💡 Hint

Bash stores exit codes of all pipeline commands in a special array variable.

The special array ${PIPESTATUS[@]} holds exit codes of all commands in the last pipeline executed.