Practical Examples of Common Linux Commands

Here are some practical examples demonstrating the usage of common Linux commands:

1. find

Finding files with specific criteria:

  • Find all files in the current directory and its subdirectories named "config.txt":

find . -name "config.txt"

  • Find all files in the current directory and its subdirectories modified in the last 24 hours:

find . -mtime -1

  • Find all files in the current directory and its subdirectories with the "txt" extension:

find . -name "*.txt"

Using find with -exec to execute commands:

  • Delete all files in the current directory and its subdirectories older than 30 days:

find . -mtime +30 -exec rm {} \;

  • Rename all files in the current directory and its subdirectories ending with ".bak" to ".txt":

find . -name "*.bak" -exec mv {} echo {} \| sed \'s/\\.bak\$/.txt/\' \;

Using find with -0 for piping:

  • Find all .txt files in the current directory and its subdirectories, then print their file sizes:

find . -name "*.txt" -print0 | xargs -0 du -h

2. tar

Creating an archive:

  • Archive all files in the current directory into a file named "my_archive.tar":

tar -cf my_archive.tar *

  • Archive all files in the "documents" directory into a file named "documents.tar", showing progress:

tar -cvf documents.tar documents/*

  • Create a compressed archive of all files in the "pictures" directory:

tar -czvf pictures.tar.gz pictures/

Extracting an archive:

  • Extract the contents of "my_archive.tar" to the current directory:

tar -xf my_archive.tar

  • Extract the contents of "documents.tar.gz" to the "extracted" directory:

tar -xzvf documents.tar.gz -C extracted

Directory Structure of tar Archives:

If you cd into a directory and then use tar -cf archive.tar * to create an archive, the resulting archive will have a structure that reflects the relative paths of the files within the directory. For example, if your directory structure is:

directory/

  • file1.txt

  • subdirectory/

  • file2.txt

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The archive.tar will have a similar structure when extracted:

extracted/

  • file1.txt

  • subdirectory/

  • file2.txt

content_copyUse code [with caution]{.underline}.

3. zip

Creating an archive:

  • Zip all files in the current directory into "my_archive.zip":

zip -r my_archive.zip *

  • Zip the contents of the "documents" directory into "documents.zip":

zip -r documents.zip documents/

Extracting an archive:

  • Extract the contents of "my_archive.zip" to the current directory:

unzip my_archive.zip

  • Extract the contents of "documents.zip" to the "extracted" directory:

unzip -d extracted documents.zip

4. for

Looping through files:

  • Print the names of all files in the current directory:

for file in *; do

echo "$file"

done

  • Create a backup of all .txt files in the current directory:

for file in *.txt; do

cp "$file" "$file.bak"

done

Looping through numbers:

  • Print numbers from 1 to 10:

for i in {1..10}; do

echo "$i"

done

  • Execute a command 5 times with a 2-second delay between each execution:

for i in {1..5}; do

echo "Executing command..."

sleep 2

done

5. touch

  • Create a new empty file named "new_file.txt":

touch new_file.txt

`

  • Update the modification time of "important_file.txt" to the current time:

touch important_file.txt

6. EOF

Multiline strings in shell scripts:

#!/bin/bash

message="This is a multiline

string with variables: $HOME"

echo "$message"

cat << EOF

This is another multiline

string.

EOF

7. pwd

  • Print the current working directory:This is useful when you want to debug where you're currently at. If you're writing some commands and they look like they're not working, for example.

pwd

8. sleep

  • Wait for 5 seconds:

sleep 5

  • Wait for 10 minutes:

sleep 10m

  • Wait for 2.5 hours:

sleep 2.5h

9. apt-get

  • Update the package list:

apt-get update

  • Install the "vim" package without prompting:

apt-get -y install vim

  • Install multiple packages:

apt-get -y install vim curl git

10. ln

  • Create a symbolic link named "my_link" pointing to the file "important_file.txt":

ln -s important_file.txt my_link

11. df

  • Show free disk space for all mounted filesystems:It's useful if your runner is running out of space and you want to do some debugging, for example.

df -h

  • Show free disk space for the "/home" filesystem:

df -h /home

12. unzip

  • Unzip the contents of "my_archive.zip" to the current directory:

unzip my_archive.zip

  • Unzip the contents of "documents.zip" to the "extracted" directory:

unzip -d extracted documents.zip

13. grep

  • Find lines containing the word "error" in the file "log.txt":

grep "error" log.txt

  • Find lines containing the pattern "error[0-9]+" (error followed by one or more digits) in the file "log.txt":

grep "error[0-9]+" log.txt

  • Find lines in all files in the current directory that contain the word "warning":

grep "warning" *