which and whereis for commands in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of which command

What is the output of the command which ls on a typical Linux system?

Linux CLI

which ls

A /bin/ls

B ls: command not found

C /usr/bin/which

D /usr/local/bin/ls

💡 Hint

The which command shows the full path of the executable that runs when you type a command.

The which command searches your PATH and shows the location of the executable. Usually, ls is in /bin.

💻 Command Output

intermediate

Output of whereis command

What does the command whereis python3 typically output?

Linux CLI

whereis python3

A python3: command not found

B python3: /usr/bin/python3 /usr/lib/python3 /usr/share/man/man1/python3.1.gz

C /bin/python3

D /usr/local/bin/python3

💡 Hint

The whereis command shows locations of the binary, source, and manual files.

The whereis command searches standard locations for binaries, source code, and man pages related to the command.

🧠 Conceptual

advanced

Difference between which and whereis

Which statement correctly describes the difference between which and whereis commands?

A <code>which</code> shows source code location; <code>whereis</code> shows only the executable path.

B <code>which</code> searches all system directories; <code>whereis</code> only searches the current directory.

C <code>which</code> shows the path of the executable found in PATH; <code>whereis</code> shows locations of binary, source, and man files.

D <code>which</code> and <code>whereis</code> are identical and interchangeable.

💡 Hint

Think about what each command searches for and where.

which finds the executable in your PATH. whereis looks for binaries, source files, and manual pages in standard system locations.

🔧 Debug

advanced

Why does which fail to find a command?

You run which myscript but get no output, even though myscript runs fine when you type it. Why?

A The script is not in any directory listed in the PATH environment variable.

B The script has no execute permission.

C The which command is broken and needs reinstalling.

D The script is a shell alias or function, not an executable file.

💡 Hint

Think about what which can find and what it cannot.

which only finds executables in PATH. It does not find shell aliases or functions, which can run but are not files.

🚀 Application

expert

Using which and whereis in a script

You want a script to check if the git command is installed and print its path. Which snippet correctly does this?

A if which git > /dev/null; then echo "Git found"; else echo "Git not found"; fi

B if path=$(which git); then echo "Git found at $path"; else echo "Git not found"; fi

C if [ $(which git) ]; then echo "Git found"; else echo "Git not found"; fi

D if whereis git; then echo "Git found"; else echo "Git not found"; fi

💡 Hint

Think about how to check command success and suppress output.

Option A correctly uses which git and checks its exit status, suppressing output. This is the best way to test if git is installed.