Looping over files and directories in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this script when run in a directory with files a.txt, b.txt, and c.log?

Consider this bash script:

for file in *.txt; do echo "$file"; done

What will it print?

Bash Scripting

for file in *.txt; do echo "$file"; done

A *.txt

B

a.txt
b.txt

C

a.txt
b.txt
c.log

D

a.txt
b.txt
*.txt

💡 Hint

The wildcard *.txt matches only files ending with .txt.

The loop iterates over files matching the pattern *.txt, so it prints only a.txt and b.txt, not c.log or the literal '*.txt'.

💻 Command Output

intermediate

What does this script output if the directory contains subdirectories dir1 and dir2?

Given this script:

for entry in *; do if [ -d "$entry" ]; then echo "$entry"; fi; done

What will it print?

Bash Scripting

for entry in *; do if [ -d "$entry" ]; then echo "$entry"; fi; done

A

dir1
dir2

B

dir1
dir2
file.txt

C *.txt

D file.txt

💡 Hint

The test -d checks if the entry is a directory.

The loop lists all entries, but only prints those that are directories, so it prints dir1 and dir2 only.

📝 Syntax

advanced

Which option correctly loops over all .log files and prints their names?

Choose the correct bash loop syntax to print all .log files in the current directory.

A for file in *.log; do echo $file; done

B for file in *.log { echo $file; }

C for (file in *.log); do echo $file; done

D foreach file in *.log; do echo $file; done

💡 Hint

Bash uses 'for var in list; do ... done' syntax.

Option A uses correct bash syntax. Options B, C, and D use invalid syntax causing errors.

🚀 Application

advanced

How to count the number of files (not directories) in the current directory using a loop?

You want to count files only (exclude directories). Which script correctly does this?

A

count=0
for item in *; do count=$((count+1)); done
echo $count

B

count=0
for item in *; do if [ -d "$item" ]; then count=$((count+1)); fi; done
echo $count

C

count=0
for item in *; do if [ -f "$item" ]; then count=$((count+1)); fi; done
echo $count

D

count=0
for item in *; do if [ -e "$item" ]; then count=$((count+1)); fi; done
echo $count

💡 Hint

Use -f to test if an entry is a regular file.

Option C counts only files. B counts directories, C counts all entries, D counts all existing entries including directories.

🔧 Debug

expert

Why does this script fail to print filenames with spaces correctly?

Script:

for file in $(ls *.txt); do echo "$file"; done

What is the problem?

Bash Scripting

for file in $(ls *.txt); do echo "$file"; done

A It loops over directories instead of files

B It does not expand *.txt pattern

C It causes a syntax error due to missing quotes

D It splits filenames on spaces, so multi-word names break into parts

💡 Hint

Command substitution splits output by spaces and newlines.

Using $(ls *.txt) splits filenames on spaces, breaking names with spaces into multiple words. Using 'for file in *.txt' is safer.