Unix – Important Commands with Useage #

1. File and Directory Management Commands #

ls #

• Usage: Lists files and directories.
• Syntax: ls [options] [path]
• Example:
  • ls: List files in the current directory.
  • ls -l: List files in long format with details like permissions, owner, size, etc.
  • ls -a: List all files, including hidden files.

cd #

• Usage: Changes the current directory.
• Syntax: cd [directory]
• Example:
  • cd /home/user: Change to the specified directory.
  • cd ..: Move to the parent directory.
  • cd ~: Move to the home directory.

pwd #

• Usage: Prints the current working directory.
• Syntax: pwd
• Example: pwd

mkdir #

• Usage: Creates a new directory.
• Syntax: mkdir [options] directory_name
• Example:
  • mkdir my_folder: Creates a directory named my_folder.
  • mkdir -p dir1/dir2: Creates nested directories.

rm #

• Usage: Removes files or directories.
• Syntax: rm [options] file_or_directory
• Example:
  • rm file.txt: Deletes file.txt.
  • rm -r folder: Deletes a directory and its contents recursively.

rmdir #

• Usage: Removes an empty directory.
• Syntax: rmdir directory_name
• Example: rmdir empty_folder

cp #

• Usage: Copies files or directories.
• Syntax: cp [options] source destination
• Example:
  • cp file1.txt file2.txt: Copies file1.txt to file2.txt.
  • cp -r folder1 folder2: Copies folder1 to folder2 recursively.

mv #

• Usage: Moves or renames files or directories.
• Syntax: mv [options] source destination
• Example:
  • mv file1.txt file2.txt: Renames or moves file1.txt to file2.txt.

2. File Viewing Commands #

cat #

• Usage: Displays the content of a file.
• Syntax: cat [options] file
• Example:
  • cat file.txt: Displays the content of file.txt.
  • cat file1.txt file2.txt > merged.txt: Concatenates two files into a new file.

more #

• Usage: Displays file content page by page.
• Syntax: more [file]
• Example: more file.txt

less #

• Usage: Displays file content, allowing navigation.
• Syntax: less [file]
• Example: less file.txt

head #

• Usage: Displays the first few lines of a file.
• Syntax: head [options] file
• Example: head -n 10 file.txt (Shows the first 10 lines).

tail #

• Usage: Displays the last few lines of a file.
• Syntax: tail [options] file
• Example: tail -n 10 file.txt (Shows the last 10 lines).

3. File Permission and Ownership Commands #

chmod #

• Usage: Changes file permissions.
• Syntax: chmod [options] mode file
• Example:
  • chmod 755 file.txt: Sets read, write, and execute for owner; read and execute for group and others.

chown #

• Usage: Changes file ownership.
• Syntax: chown [owner][:group] file
• Example: chown user:group file.txt

chgrp #

• Usage: Changes group ownership.
• Syntax: chgrp [group] file
• Example: chgrp group file.txt

4. Process Management Commands #

ps #

• Usage: Displays information about active processes.
• Syntax: ps [options]
• Example:
  • ps: Displays processes for the current shell.
  • ps -ef: Displays all running processes.

top #

• Usage: Shows real-time processes and system resource usage.
• Syntax: top

kill #

• Usage: Terminates a process by PID.
• Syntax: kill [signal] PID
• Example: kill -9 12345

jobs #

• Usage: Lists background jobs.
• Syntax: jobs

fg #

• Usage: Brings a background job to the foreground.
• Syntax: fg [job_id]

bg #

• Usage: Resumes a suspended job in the background.
• Syntax: bg [job_id]

5. Networking Commands #

ping #

• Usage: Checks connectivity to a host.
• Syntax: ping [options] host
• Example: ping google.com

netstat #

• Usage: Displays network connections and statistics.
• Syntax: netstat [options]

curl #

• Usage: Transfers data from or to a server.
• Syntax: curl [options] URL
• Example: curl https://example.com

wget #

• Usage: Downloads files from the web.
• Syntax: wget [options] URL
• Example: wget https://example.com/file.txt

scp #

• Usage: Copies files between hosts.
• Syntax: scp [options] source destination
• Example: scp file.txt user@host:/path/to/destination

ssh #

• Usage: Logs into a remote machine securely.
• Syntax: ssh user@host
• Example: ssh user@192.168.1.1

6. Disk Usage Commands #

df #

• Usage: Displays disk space usage.
• Syntax: df [options]
• Example: df -h (Shows human-readable format).

du #

• Usage: Displays directory or file space usage.
• Syntax: du [options] [path]
• Example: du -sh folder/

7. Search and Filter Commands #

grep #

• Usage: Searches for a pattern in files.
• Syntax: grep [options] pattern file
• Example:
  • grep 'hello' file.txt: Searches for ‘hello’ in file.txt.
  • grep -r 'error' /var/logs: Searches recursively for ‘error’ in /var/logs.

find #

• Usage: Searches for files and directories.
• Syntax: find [path] [options]
• Example:
  • find . -name "*.txt": Finds all .txt files in the current directory.
  • find /home -size +100M: Finds files larger than 100MB.

awk #

• Usage: Processes and analyzes text.
• Syntax: awk 'pattern {action}' file
• Example: awk '{print $1}' file.txt: Prints the first column of a file.

sed #

• Usage: Edits text in a file or stream.
• Syntax: sed 'script' file
• Example: sed 's/old/new/g' file.txt: Replaces ‘old’ with ‘new’.

8. Archiving and Compression Commands #

tar #

• Usage: Archives files and directories.
• Syntax: tar [options] archive_name file_or_directory
• Example: tar -cvf archive.tar folder

gzip #

• Usage: Compresses files.
• Syntax: gzip [file]
• Example: gzip file.txt

unzip #

• Usage: Extracts ZIP files.
• Syntax: unzip file.zip

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This list provides an essential toolkit for working effectively in a Unix environment. Mastering these commands can significantly enhance your productivity and proficiency!