Portable scripting (POSIX compliance) in Bash Scripting - Mini Project: Build & Apply

Portable scripting (POSIX compliance)

📖 Scenario: You work as a system administrator who needs to write scripts that run on many different Unix-like systems. Some systems have different shells or tools. To avoid errors, you want to write scripts that follow POSIX standards. This means your script will work on most systems without changes.

🎯 Goal: You will create a simple POSIX-compliant shell script that lists files in a directory, counts how many files there are, and prints the count. This script will use only POSIX features to ensure it runs everywhere.

📋 What You'll Learn

Create a shell script using only POSIX-compliant commands and syntax

Use ls to list files in a directory

Use a POSIX-compliant loop to count files

Print the total count using printf for portability

💡 Why This Matters

🌍 Real World

System administrators and developers often need scripts that run on many different Unix-like systems. Writing POSIX-compliant scripts ensures compatibility and reduces errors.

💼 Career

Knowing how to write portable shell scripts is valuable for roles in system administration, DevOps, and automation where scripts must work across diverse environments.

1

Create a POSIX-compliant shell script header and list files

Write the first line of the script as #!/bin/sh to specify the POSIX shell. Then create a variable called files that stores the output of ls command listing files in the current directory.

Bash Scripting

# Write the POSIX shell header and assign the output of ls to files
# Your code here

Need a hint?

The first line #!/bin/sh tells the system to use the POSIX shell. Use $(ls) to capture the output of the ls command.

2

Add a counter variable to count files

Add a variable called count and set it to 0. This will keep track of how many files are in the directory.

Bash Scripting

#!/bin/sh
files=$(ls)
# Initialize count variable
# Your code here

Need a hint?

Just write count=0 to start counting from zero.

3

Use a POSIX-compliant loop to count files

Use a for loop with the variable file to iterate over each item in $files. Inside the loop, increase count by 1 using POSIX syntax.

Bash Scripting

#!/bin/sh
files=$(ls)
count=0
# Loop over files and increment count
# Your code here

Need a hint?

Use for file in $files; do ... done and increment count with count=$((count + 1)).

4

Print the total count using printf

Use printf to print the message Total files: X where X is the value of count. This ensures portable output formatting.

Bash Scripting

#!/bin/sh
files=$(ls)
count=0
for file in $files; do
    count=$((count + 1))
done
# Print the total count
# Your code here

Need a hint?

Use printf "Total files: %d\n" "$count" to print the count.