File existence checks in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the file '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-f

B-d

C-e

D-s

Attempts:

3 left

💡 Hint

Common Mistakes

Using -d which checks only for directories.

Using -f which checks only for regular files.

Using -s which checks if file exists and is not empty.

The -e option checks if a file or directory exists.

2fill in blank

medium

Complete the code to check if 'log.txt' is a regular file.

Bash Scripting

if [ [1] "log.txt" ]; then
  echo "It's a regular file"
fi

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

A-f

B-e

C-d

D-r

Attempts:

3 left

💡 Hint

Common Mistakes

Using -d which checks for directories.

Using -e which checks for any file or directory.

Using -r which checks if file is readable.

The -f option checks if the file exists and is a regular file (not a directory).

3fill in blank

hard

Fix the error in the code to check if 'folder' is a directory.

Bash Scripting

if [ [1] "folder" ]; then
  echo "It's a directory"
fi

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

A-f

B-d

C-e

D-s

Attempts:

3 left

💡 Hint

Common Mistakes

Using -f which checks for regular files.

Using -e which checks for any file or directory.

Using -s which checks if file is not empty.

The -d option checks if the path is a directory.

4fill in blank

hard

Fill both blanks to check if 'script.sh' exists and is executable.

Bash Scripting

if [ [1] "script.sh" ] && [ [2] "script.sh" ]; then
  echo "Script is ready to run"
fi

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

A-e

B-x

C-f

D-r

Attempts:

3 left

💡 Hint

Common Mistakes

Using -e instead of -f to check for regular file.

Using -r instead of -x to check for executable permission.

-f checks if it is a regular file, and -x checks if it is executable.

5fill in blank

hard

Fill all three blanks to create a dictionary of files and their sizes if size is greater than 0.

Bash Scripting

declare -A file_sizes
for file in *; do
  if [ [1] "$file" ] && [ $( [2] "$file" ) -gt 0 ]; then
    file_sizes[[3]]=$(stat -c%s "$file")
  fi
done

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

A-f

Bstat -c%s

C$file

D-s

Attempts:

3 left

💡 Hint

Common Mistakes

Using -f instead of -s to check file size.

Using filename incorrectly as dictionary key.

Not using stat command to get file size.

-s checks if file size is greater than zero, stat -c%s gets file size, and $file is the key in the dictionary.

Practice

1. Which command correctly checks if a file named data.txt exists in a bash script?

easy

A. if [ -e data.txt ]; then echo "File exists"; fi

B. if ( -e data.txt ); then echo "File exists"; fi

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

D. if test -f data.txt then echo "File exists"; fi

Solution

1. Step 1: Understand the correct syntax for file existence check

   The test command with square brackets and -e checks if a file or directory exists.

2. Step 2: Verify the command structure

   The command if [ -e data.txt ]; then ... fi is the correct syntax in bash for this check.

3. Final Answer:

   if [ -e data.txt ]; then echo "File exists"; fi -> Option A

4. Quick Check:

   Use [ -e filename ] to check existence [OK]

Hint: Use [ -e filename ] inside if for existence check [OK]

Common Mistakes:

• Using parentheses instead of square brackets
• Using incorrect test operators like 'exists'
• Missing semicolon or then keyword

2. Which of the following is the correct syntax to check if a file report.log exists and is a regular file in bash?

easy

A. if [ -d report.log ]; then echo "Exists"; fi

B. if [ -f report.log ]; then echo "Exists"; fi

C. if [ -e report.log ]; then echo "Exists"; fi

D. if test -x report.log; then echo "Exists"; fi

Solution

1. Step 1: Identify the test for regular file

   The -f option checks if the file exists and is a regular file (not directory).

2. Step 2: Confirm the syntax

   The syntax if [ -f report.log ]; then ... fi correctly checks for a regular file.

3. Final Answer:

   if [ -f report.log ]; then echo "Exists"; fi -> Option B

4. Quick Check:

   -f checks regular file existence [OK]

Hint: Use [ -f filename ] to check regular file existence [OK]

Common Mistakes:

• Using -d which checks for directories
• Using -x which checks for executable permission
• Confusing -e (exists) with -f (regular file)

3. What will be the output of this script if myfile.txt does not exist?

if [ -e myfile.txt ]; then
  echo "Found"
else
  echo "Not Found"
fi

medium

A. Not Found

B. Syntax error

C. Found

D. No output

Solution

1. Step 1: Understand the condition

   The condition [ -e myfile.txt ] checks if the file exists.

2. Step 2: Evaluate the file existence

   Since myfile.txt does not exist, the condition is false, so the else branch runs.

3. Final Answer:

   Not Found -> Option A

4. Quick Check:

   File missing triggers else branch [OK]

Hint: If file missing, else branch runs [OK]

Common Mistakes:

• Assuming output is 'Found' even if file missing
• Confusing -e with other test operators
• Missing else branch handling

4. Identify the error in this bash snippet that checks if config.cfg exists:

if [ -e config.cfg ]
  echo "Exists"
fi

medium

A. Echo command syntax is wrong

B. Wrong test operator -e used

C. Missing closing bracket ]

D. Missing then keyword after condition

Solution

1. Step 1: Check if statement syntax

   Bash requires the then keyword after the condition in an if statement.

2. Step 2: Identify missing part

   The snippet lacks then after [ -e config.cfg ], causing a syntax error.

3. Final Answer:

   Missing then keyword after condition -> Option D

4. Quick Check:

   if needs then after condition [OK]

Hint: Always put then after if condition [OK]

Common Mistakes:

• Omitting then keyword
• Forgetting semicolon before then on same line
• Misplacing brackets

5. You want to write a bash script that checks if a file named backup.tar.gz exists, and if it does, prints "Backup found", otherwise creates an empty file with that name. Which script snippet correctly does this?

hard

A. if [ -e backup.tar.gz ]; then touch backup.tar.gz; else echo "Backup found"; fi

B. if [ -f backup.tar.gz ]; then touch backup.tar.gz; else echo "Backup found"; fi

C. if [ -e "backup.tar.gz" ]; then echo "Backup found"; else touch backup.tar.gz; fi

D. if test -d backup.tar.gz; then echo "Backup found"; else touch backup.tar.gz; fi

Solution

1. Step 1: Check file existence correctly

   Use [ -e "backup.tar.gz" ] to check if the file exists, quoting filename to handle spaces.

2. Step 2: Execute correct commands based on condition

   If file exists, print "Backup found"; else create empty file with touch.

3. Final Answer:

   if [ -e "backup.tar.gz" ]; then echo "Backup found"; else touch backup.tar.gz; fi -> Option C

4. Quick Check:

   Check existence then else create file [OK]

Hint: Quote filenames and use if-else for existence and creation [OK]

Common Mistakes:

• Swapping then and else commands
• Using -d to check regular files
• Not quoting filenames with spaces