Temporary files (mktemp) in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this mktemp command?

Consider the following command run in a bash shell:

mktemp /tmp/tempfile.XXXXXX

What does this command output?

Bash Scripting

mktemp /tmp/tempfile.XXXXXX

A The literal string '/tmp/tempfile.XXXXXX' without changes

B A unique temporary filename starting with /tmp/tempfile. followed by 6 random characters

C A directory named tempfile.XXXXXX created in /tmp

D An error message because mktemp requires no arguments

💡 Hint

mktemp replaces the XXXXXX with random characters to create a unique filename.

The mktemp command creates a unique temporary file or directory. When given a template with Xs, it replaces them with random characters to avoid name collisions.

💻 Command Output

intermediate

What error does this mktemp command produce?

What error message will this command produce?

mktemp /tmp/tempfile

Note: The template does not contain any 'X' characters.

Bash Scripting

mktemp /tmp/tempfile

A mktemp: too few X's in template '/tmp/tempfile'

B No error, creates a file named /tmp/tempfile

C mktemp: cannot create temporary file

D mktemp: invalid option -- 't'

💡 Hint

mktemp requires at least 3 'X' characters in the template to replace.

The mktemp command expects a template with at least 3 'X' characters to generate a unique name. Without them, it throws an error about too few X's.

🔧 Debug

advanced

Why does this mktemp command fail to create a file?

Given this command:

mktemp -d /tmp/mydir.XXXXXX

It fails with an error 'cannot create directory'. What is the most likely reason?

Bash Scripting

mktemp -d /tmp/mydir.XXXXXX

A The -d option is invalid and causes failure

B The template must not contain any X characters when using -d

C The /tmp directory does not exist or is not writable

D mktemp cannot create directories, only files

💡 Hint

Check if the directory where you want to create the temp directory exists and is writable.

The -d option tells mktemp to create a directory. If /tmp does not exist or you lack permissions, mktemp cannot create the directory and fails.

🚀 Application

advanced

Which script snippet safely creates and cleans up a temporary file?

You want to create a temporary file, write 'Hello' into it, then delete it after use. Which snippet does this correctly?

A tmpfile=$(mktemp) && echo 'Hello' > "$tmpfile" && cat "$tmpfile" && rm "$tmpfile"

B tmpfile=mktemp && echo 'Hello' > $tmpfile && cat $tmpfile && rm $tmpfile

C mktemp > tmpfile && echo 'Hello' > tmpfile && cat tmpfile && rm tmpfile

D tmpfile=$(mktemp) && echo 'Hello' > tmpfile && cat tmpfile && rm tmpfile

💡 Hint

Remember to capture the output of mktemp in a variable and quote variables when used.

Option A correctly captures the temporary filename in a variable, uses quotes to handle spaces, writes to the file, reads it, then removes it. Others either miss command substitution or quoting.

🧠 Conceptual

expert

Why is mktemp preferred over manual temp file naming?

Why should scripts use mktemp to create temporary files instead of manually naming files like /tmp/tempfile.txt?

A Manual naming automatically cleans up files after use

B Manual naming is faster and more secure than mktemp

C mktemp creates files with fixed names for easier debugging

D mktemp guarantees unique filenames and avoids race conditions

💡 Hint

Think about what happens if two scripts use the same temp filename.

mktemp creates unique filenames safely, preventing conflicts and security issues like race conditions. Manual naming risks overwriting files or security holes.