File Compression and File Permissions in Bash: A Complete Guide for Beginners

Introduction

When working with Linux or any Unix-based system, Bash (Bourne Again Shell) is your ultimate command-line companion. Whether you are managing files, automating backups, or securing system access, understanding file compression and file permissions is essential.

This article dives deep into two critical aspects of Bash:

1. File Compression – efficiently storing and transferring data.
2. File Permissions – controlling who can access or modify your files.

Let’s explore each section with practical commands and real-world use cases.

Explore:

• Basic Bash Commands Explained for Beginners (with Examples)

• Networking in Bash: Essential Commands for Connectivity and File Transfer

File Compression in Bash

File compression helps save disk space and makes it easier to share or back up files. Bash offers several tools to compress and extract files — the most common being zip, unzip, and tar.

1. Bash Compress (zip)

The zip command compresses files or directories into a single .zip archive.

Syntax:

zip [options] archive_name.zip file1 file2 ...

Example:

zip myfiles.zip report.txt data.csv script.sh

This command creates a compressed archive named myfiles.zip containing the three files.

To compress an entire directory:

zip -r project.zip /home/user/project

• -r means recursive, so all files and subdirectories inside /project are included.

Useful Options:

• -r – Recursively include subdirectories.
• -q – Quiet mode (no output).
• -9 – Maximum compression.
• -e – Encrypt archive with a password.

Example with encryption:

zip -e backup.zip confidential.txt

2. Bash Extract (unzip)

The unzip command extracts the contents of a .zip file.

Syntax:

unzip [options] archive_name.zip

Example:

unzip myfiles.zip

This extracts all files in the current directory.

Extract to a specific directory:

unzip myfiles.zip -d /home/user/extracted/

List contents without extracting:

unzip -l myfiles.zip

Useful Options:

• -d – Specify extraction directory.
• -l – List contents.
• -q – Quiet mode.

3. Bash TAR Archive

The tar command (short for Tape Archive) is one of the most powerful tools in Linux for file archiving and compression.

It supports multiple compression formats like .tar, .tar.gz, .tar.bz2, and .tar.xz.

Syntax:

tar [options] archive_name.tar file1 file2 ...

Create an uncompressed archive:

tar -cvf archive.tar file1.txt file2.txt

• -c → Create archive
• -v → Verbose output
• -f → Filename of archive

Extract a TAR archive:

tar -xvf archive.tar

• -x → Extract files

Create a compressed GZIP archive:

tar -czvf archive.tar.gz /home/user/documents/

Extract a .tar.gz file:

tar -xzvf archive.tar.gz

Create a BZIP2 compressed archive:

tar -cjvf archive.tar.bz2 /var/log/

Extract a .tar.bz2 file:

tar -xjvf archive.tar.bz2

List contents without extracting:

tar -tvf archive.tar.gz

Summary Table:

Task	Command Example
Create TAR	tar -cvf archive.tar file1 file2
Extract TAR	tar -xvf archive.tar
Create TAR.GZ	tar -czvf archive.tar.gz dir/
Extract TAR.GZ	tar -xzvf archive.tar.gz
List TAR Contents	tar -tvf archive.tar

File Permissions in Bash

File permissions in Linux determine who can read, write, or execute a file. Every file and directory has associated permissions and ownership.

Let’s break it down.

1. Understanding Permission Structure

Run the ls -l command to view permissions:

ls -l

Output:

-rwxr-xr-- 1 user group 2048 Oct 25 10:00 script.sh

Explanation:

• -rwxr-xr--
  • r → read
  • w → write
  • x → execute
• Three sets of permissions:
  • Owner (user): rwx
  • Group: r-x
  • Others: r--

2. Bash Modify (chmod)

The chmod command changes file permissions.

Syntax:

chmod [options] mode file_name

Symbolic method:

chmod u+x script.sh

Adds execute (x) permission for the user (owner).

Numeric method:

Each permission has a numeric value:

• Read = 4
• Write = 2
• Execute = 1

Add them for combined permissions:

• rwx = 7
• rw- = 6
• r-- = 4

Example:

chmod 755 script.sh

• User: 7 (rwx)
• Group: 5 (r-x)
• Others: 5 (r-x)

Remove write permission for others:

chmod o-w data.txt

Recursive permission change:

chmod -R 755 /home/user/project/

3. Bash Ownership (chown)

The chown command changes the ownership of a file or directory.

Syntax:

chown [options] new_owner file_name

Example:

chown harshvardhan report.txt

Changes the file owner to harshvardhan.

Change both owner and group:

chown harshvardhan:developers project/

Recursive ownership change:

chown -R harshvardhan:admin /var/www/

4. Bash Group (chgrp)

The chgrp command changes the group ownership of a file.

Syntax:

chgrp [options] group_name file_name

Example:

chgrp developers main.c

Recursive group change:

chgrp -R admins /opt/server/

Common Ownership & Permission Tasks

Task	Command
Change file permissions	chmod 644 file.txt
Make script executable	chmod +x script.sh
Change file owner	chown user file.txt
Change file group	chgrp team file.txt
Change both owner & group	chown user:group file.txt

Best Practices

• Always verify ownership before modifying permissions on system files.
• Use least privilege principle — grant only necessary permissions.
• For shared directories, set group ownership properly using chown or chgrp.
• Use chmod -R carefully — it can expose or break critical system files if applied incorrectly.
• Combine compression (tar, zip) and permission commands for backup automation.

Conclusion

Mastering file compression and file permissions in Bash empowers you to manage files efficiently and securely. Whether you are automating backups with tar or setting proper access with chmod and chown, these commands are foundational for every Linux user, developer, or system administrator.

By practicing these Bash commands, you’ll gain the confidence to control your system resources like a true Linux professional.