Erstellen von Shell-Skripten mit Schleifen

Introduction

In this challenge, you will learn how to create a simple shell script that uses looping constructs (such as for and while) to process file or command-line input. Shell scripting is a powerful tool for automating repetitive tasks and streamlining your workflow. By completing this challenge, you will gain hands-on experience in developing shell scripts that can handle dynamic input and perform various operations.

Create a Shell Script with a for Loop

In this step, you will create a shell script that uses a for loop to iterate through a list of files in a directory and perform an operation on each file. This script will demonstrate how to process multiple files dynamically, which is a common task in shell scripting.

Tasks

• Create a shell script that uses a for loop to iterate through a list of files in a specified directory.
• For each file found, the script should print the file's name and its contents.

Requirements

• The script must be named list_files.sh.
• The script must be located in the ~/project directory.
• The script must start with the #!/bin/bash shebang.
• The script must accept a directory path as its first command-line argument.
• The script must use a for loop to iterate through the files within the provided directory.
• For each regular file encountered, the script must print "File: " followed by the file's base name, and then print the entire content of the file.
• If no directory argument is provided, the script should print a usage message and exit with a non-zero status code.

Example

Let's assume you have created the list_files.sh script in ~/project and made it executable. When you run it with ~/project as the argument, the output should look similar to this:

[labex@host ~]$ cd ~/project
[labex@host project]$ chmod +x list_files.sh
[labex@host project]$ ./list_files.sh ~/project
File: file1.txt
Content of file1.txt

File: file2.txt
Content of file2.txt

File: file3.txt
Content of file3.txt

[labex@host project]$

If you run the script without any arguments, it should display a usage message:

[labex@host project]$ ./list_files.sh
Usage: ./list_files.sh <directory_path>
[labex@host project]$ echo $?
1
[labex@host project]$

The exact content of the files will depend on what you put in them.

Hints

• You can use the special variable $1 to access the first command-line argument passed to your script.
• To iterate through files in a directory, you can use a wildcard pattern like "$1"/*.
• Use an if statement with the -f test operator (e.g., if [ -f "$file" ]) to check if an item is a regular file and not a directory.
• The basename command can be useful to extract just the file name from a full path. For example, basename /home/labex/project/file1.txt would output file1.txt.
• The cat command can be used to display the contents of a file.
• Remember to make your script executable using chmod +x.
• To check if a variable is empty, you can use if [ -z "$variable" ].
• To exit a script with a specific status code, use exit <status_code>.

Summary

In this challenge, you learned how to create a simple shell script that uses a for loop to iterate through files in a directory and perform operations on them. You practiced accepting command-line arguments, validating input, and using conditional statements (if) to process only regular files. You also used basename to extract file names and cat to display file contents. These skills are fundamental for automating tasks, processing data, and managing files efficiently in a Linux environment, which are essential for RHCSA certification and daily system administration.