File test operators (-f, -d, -e, -r, -w, -x) in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a file named 'data.txt' exists.

Bash Scripting

if [ [1] data.txt ]; then
  echo "File exists."
fi

Drag options to blanks, or click blank then click option'

A-d

B-f

C-r

D-w

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-d' which checks for directories instead of files.

Using '-r' or '-w' which check permissions, not existence.

The '-f' operator checks if the file exists and is a regular file.

2fill in blank

medium

Complete the code to check if the directory '/home/user/docs' exists.

Bash Scripting

if [ [1] /home/user/docs ]; then
  echo "Directory exists."
fi

Drag options to blanks, or click blank then click option'

A-d

B-f

C-e

D-x

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-f' which checks for regular files, not directories.

Using '-e' which checks existence but not specifically for directories.

The '-d' operator checks if the path exists and is a directory.

3fill in blank

hard

Fix the error in the code to check if the file 'script.sh' is executable.

Bash Scripting

if [ [1] script.sh ]; then
  echo "File is executable."
fi

Drag options to blanks, or click blank then click option'

A-f

B-r

C-w

D-x

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-r' or '-w' which check read or write permissions instead.

Using '-f' which checks if it is a regular file but not executable.

The '-x' operator checks if the file is executable.

4fill in blank

hard

Fill both blanks to check if 'config.cfg' exists and is readable.

Bash Scripting

if [ [1] config.cfg ] && [ [2] config.cfg ]; then
  echo "Config exists and is readable."
fi

Drag options to blanks, or click blank then click option'

A-e

B-r

C-f

D-w

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-f' instead of '-e' for existence check.

Using '-w' instead of '-r' for read permission.

Use '-e' to check existence and '-r' to check read permission.

5fill in blank

hard

Fill all three blanks to create a dictionary of files in 'docs' directory that exist, are writable, and executable.

Bash Scripting

files_status = {file: ( [ -[1] file ] && [ -[2] file ] && [ -[3] file ]) for file in $(ls docs) }

Drag options to blanks, or click blank then click option'

Ae

Bw

Cx

Dr

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up read and write permissions.

Using '-f' instead of '-e' for existence.

Use '-e' for existence, '-w' for write permission, and '-x' for execute permission.

Practice

1. Which file test operator checks if a path is a regular file in a bash script?

easy

A. -e

B. -f

C. -d

D. -x

Solution

1. Step 1: Understand the meaning of each operator

   -f checks if the path is a regular file, -d checks for directory, -e checks if the path exists, and -x checks if the file is executable.

2. Step 2: Match the operator to the question

   The question asks for the operator that checks if a path is a regular file, which is -f.

3. Final Answer:

   -f -> Option B

4. Quick Check:

   Regular file check = -f [OK]

Hint: Remember: -f means file, -d means directory [OK]

Common Mistakes:

• Confusing -f with -d
• Using -e which only checks existence
• Mixing -x (executable) with file type

2. Which of the following is the correct syntax to check if a directory exists in bash?

easy

A. if [ -f /path/to/dir ]; then echo "Exists"; fi

B. if [ -x /path/to/dir ]; then echo "Exists"; fi

C. if [ -e /path/to/dir ]; then echo "Exists"; fi

D. if [ -d /path/to/dir ]; then echo "Exists"; fi

Solution

1. Step 1: Identify the operator for directory check

   -d is used to check if a path is a directory.

2. Step 2: Verify the syntax correctness

   The syntax if [ -d /path/to/dir ]; then ... fi is correct for checking directory existence.

3. Final Answer:

   if [ -d /path/to/dir ]; then echo "Exists"; fi -> Option D

4. Quick Check:

   Directory check uses -d [OK]

Hint: Use -d to check directories, not -f or -x [OK]

Common Mistakes:

• Using -f to check directories
• Confusing -e (exists) with directory check
• Missing spaces inside [ ] causing syntax errors

3. What will be the output of this script if myfile.txt exists and is readable but not writable?

if [ -r myfile.txt ]; then echo "Readable"; else echo "Not readable"; fi
if [ -w myfile.txt ]; then echo "Writable"; else echo "Not writable"; fi

medium

A. Readable\nWritable

B. Not readable\nWritable

C. Readable\nNot writable

D. Not readable\nNot writable

Solution

1. Step 1: Check readability condition

   The file exists and is readable, so [ -r myfile.txt ] is true, printing "Readable".

2. Step 2: Check writability condition

   The file is not writable, so [ -w myfile.txt ] is false, printing "Not writable".

3. Final Answer:

   Readable\nNot writable -> Option C

4. Quick Check:

   Readable true, writable false = A [OK]

Hint: Check each permission separately with -r and -w [OK]

Common Mistakes:

• Assuming writable if readable
• Mixing up -r and -w operators
• Ignoring else branch output

4. Identify the error in this bash snippet that checks if a file exists and is executable:

if [ -e myscript.sh -a -x ]; then echo "Executable file"; fi

medium

A. Missing filename after -x operator

B. Wrong operator -e should be -f

C. Missing spaces around -a operator

D. Should use double brackets [[ ]] instead of single [ ]

Solution

1. Step 1: Analyze the -x operator usage

   The -x operator requires a filename argument, but none is provided after it.

2. Step 2: Check other parts of the condition

   -e myscript.sh is valid to check existence; spaces around -a are correct; using single brackets is valid.

3. Final Answer:

   Missing filename after -x operator -> Option A

4. Quick Check:

   -x needs a file name [OK]

Hint: Always provide filename after each test operator [OK]

Common Mistakes:

• Forgetting filename after -x
• Confusing -e and -f operators
• Missing spaces around operators causing syntax errors

5. You want to write a bash script that prints "Ready" only if config.cfg exists, is a regular file, and is readable and writable. Which condition correctly checks all these?

hard

A. if [ -f config.cfg ] && [ -r config.cfg ] && [ -w config.cfg ]; then echo "Ready"; fi

B. if [ -e config.cfg -a -r config.cfg -a -w config.cfg ]; then echo "Ready"; fi

C. if [ -d config.cfg ] && [ -r config.cfg ] && [ -w config.cfg ]; then echo "Ready"; fi

D. if [ -e config.cfg ] && [ -r config.cfg ] && [ -w config.cfg ]; then echo "Ready"; fi

Solution

1. Step 1: Identify the operator for regular file check

   -f checks if the path is a regular file, which is required.

2. Step 2: Combine all conditions correctly

   Using && between separate [ ] tests is correct and clear. The script checks existence as a file, readability, and writability.

3. Step 3: Eliminate incorrect options

   if [ -e config.cfg ] && [ -r config.cfg ] && [ -w config.cfg ]; then echo "Ready"; fi uses -e which allows directories; if [ -e config.cfg -a -r config.cfg -a -w config.cfg ]; then echo "Ready"; fi uses -e which allows directories; if [ -d config.cfg ] && [ -r config.cfg ] && [ -w config.cfg ]; then echo "Ready"; fi checks for directory which is wrong.

4. Final Answer:

   if [ -f config.cfg ] && [ -r config.cfg ] && [ -w config.cfg ]; then echo "Ready"; fi -> Option A

5. Quick Check:

   Regular file with read/write uses -f, -r, -w combined [OK]

Hint: Use -f for file, combine tests with && for clarity [OK]

Common Mistakes:

• Using -e instead of -f to check file type
• Using -a inside single [ ] causing confusion
• Checking directory instead of file