Tuesday 2 March 2021

Top 10 Example of lsof commands in Linux and UNIX

In a Linux or UNIX operating system, there are many processes running simultaneously. These processes use files, sockets, and other resources that are managed by the operating system. To get information about these resources, we can use the "lsof" (list open files) command. Lsof is a powerful tool that can help us understand the system's state, monitor and debug applications, and troubleshoot issues. In this article, we will look at ten examples of using the lsof command in Linux and UNIX.

List all open files:

To list all the open files in the system, we can simply run the lsof command without any arguments. This will give us a comprehensive list of all the files and their corresponding processes.

lsof

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Sunday 24 March 2024

The Essential 70 Linux Commands for DevOps

In the world of DevOps, efficiency and automation are kings. This is where Linux, with its vast array of command-line tools, shines. The command line is a powerful ally, providing direct control over the operating system and the machinery that runs your applications. Here, we introduce the top 70 Linux commands that are indispensable for DevOps engineers and system administrators. These commands form the backbone of many automated tasks, troubleshooting, and daily management of systems.

File and Directory Operations

  1. ls: Unveil the contents of directories.
  2. cd: Navigate through directories.
  3. pwd: Display the current directory.
  4. mkdir: Forge new directories.
  5. touch: Create files without content.
  6. cp: Duplicate files or directories.
  7. mv: Relocate or rename files/directories.
  8. rm: Eliminate files or directories.
  9. find: Seek out files or directories.
  10. grep: Filter patterns within files.

Viewing and Manipulating Text

  1. cat: Merge and show file content.
  2. less: Read files in a paginated view.
  3. head: Peek at the beginning of files.
  4. tail: Inspect the end of files.
  5. vi/vim: Dive into text editing.
  6. nano: Simplify text editing.

File Compression and Archiving

  1. tar: Bundle files into archives.
  2. gzip: Compress files.
  3. gunzip: Decompress files.

Network Operations

  1. wget: Fetch files from the web.
  2. curl: Transfer data from or to a server.
  3. ssh: Securely connect to remote machines.
  4. scp: Copy files between hosts securely.

Permissions and Ownership

  1. chmod: Modify file permissions.
  2. chown: Change file ownership.
  3. chgrp: Adjust group ownership.

Process Management

  1. ps: List active processes.
  2. top: Monitor system resources in real-time.
  3. kill: Terminate processes.

Disk Usage and Analysis

  1. df: Show disk space usage.
  2. du: Estimate file and directory space.

System Information and Performance

  1. free: Display memory usage.
  2. uname: Output system information.
  3. ifconfig: Configure network interfaces.
  4. ping: Test the reachability of a host.
  5. netstat: Show network statistics.
  6. iptables: Manage firewall rules.
  7. systemctl: Control system services.
  8. journalctl: Examine system logs.
  9. crontab: Schedule repetitive tasks.

User and Group Management

  1. useradd: Create new user accounts.
  2. passwd: Change passwords.
  3. su: Switch between users.
  4. sudo: Execute commands with superuser privileges.
  5. usermod: Modify user accounts.
  6. groupadd: Establish new groups.
  7. groupmod: Modify group details.
  8. id: Display user/group information.

Security and Encryption

  1. ssh-keygen: Generate SSH keys.
  2. rsync: Sync files between systems securely.

File Comparison and Patching

  1. diff: Compare files line by line.
  2. patch: Apply changes to files.

Advanced Text Processing

  1. sed: Edit text in a stream.
  2. awk: Program for data extraction.
  3. sort: Arrange lines in text files.
  4. cut: Trim sections from lines.
  5. wc: Count words, lines, and characters.
  6. tee: Output to multiple files/commands.
  7. history: Review command history.
  8. source: Execute file commands in the current shell.
  9. alias: Create shortcuts for commands.
  10. ln: Link files.
  11. lsof: List open files.

System and Disk Management

  1. mkfs: Format filesystems.
  2. mount/umount: Mount or dismount filesystems.
  3. ssh-agent: Manage SSH keys.

Networking and Analysis

  1. nc: Networking utility.
  2. whois: Domain information lookup.
  3. dig: DNS lookup.

Enhancements and Utilities

  1. screen: Manage multiple terminal sessions.

By mastering these commands, DevOps professionals can harness the full potential of Linux to automate and streamline operations, troubleshoot and resolve issues swiftly, and manage systems with unparalleled efficiency. Each command, from file manipulation to system monitoring, plays a vital role in the daily life of a DevOps engineer, making this list an essential toolkit for the trade.

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Wednesday 8 July 2020

perl program to Renaming Files with a Prefix

This Perl script renames all the files in the current directory with a given prefix. The prefix can be passed as a command-line argument.

Method 1: Using rename function

#!/usr/bin/perl

my $prefix = shift @ARGV || '';

opendir my $dh, '.' or die "Couldn't open current directory: $!";

while (my $filename = readdir $dh) {

    next if $filename =~ /^\./; # Skip dotfiles

    my $newname = $prefix . $filename;

    rename $filename, $newname or warn "Couldn't rename $filename: $!";

}

closedir $dh;


or


#!/usr/bin/perl

use strict;

use warnings;

use File::Glob;


my $prefix = 'new_';

my $pattern = '*.txt';


foreach my $file (glob $pattern) {

    my $new_file = $prefix . $file;

    rename $file, $new_file or die "Can't rename $file to $new_file: $!";

}

Save the script as rename.pl and run it with perl rename.pl newprefix_. This will add the prefix "newprefix_" to all the files in the current directory.


Method 2: Using File::Copy

This method uses the File::Copy module to copy files with a new name and then delete the old file. We can use the File::Glob module to get a list of files matching a pattern and then use the File::Copy module to copy each file with the new name.

#!/usr/bin/perl

use strict;

use warnings;

use File::Glob;

use File::Copy;

my $prefix = 'new_';

my $pattern = '*.txt';

foreach my $file (glob $pattern) {

    my $new_file = $prefix . $file;

    copy $file, $new_file or die "Can't copy $file to $new_file: $!";

    unlink $file or die "Can't delete $file: $!";

}

Save the script as rename_files_method2.pl and run it with perl rename_files_method2.pl. This will rename all .txt files in the current directory with the prefix new_.


Method 3: Using regular expressions

This method uses regular expressions to modify the filenames with a prefix. We can use the File::Glob module to get a list of files matching a pattern and then use regular expressions to modify each filename.

use strict;

use warnings;


use File::Glob;

my $prefix = 'new_';

my $pattern = '*.txt';

foreach my $file (glob $pattern) {

    my $new_file = $file;

    $new_file =~ s/^/$prefix/;

    rename $file, $new_file or die "Can't rename $file to $new_file: $!";

}

Save the script as rename_files_method3.pl and run it with `perl rename_files

all .txt files in the current directory with the prefix new_.


Method 4: Using File::Find

This method uses the File::Find module to recursively find and rename files with a prefix. The File::Find module provides a way to traverse a directory tree and apply a function to each file found. We can use the rename function within the wanted function to rename each file with the specified prefix.

#!/usr/bin/perl

use strict;

use warnings;

use File::Find;

my $prefix = 'new_';


sub rename_file {

    if (-f && /^.*\.txt$/) {

        my $new_file = $prefix . $_;

        rename $_, $new_file or warn "Can't rename $_ to $new_file: $!";

    }

}

find(\&rename_file, '.');

Save the script as rename_files_method4.pl and run it with perl rename_files_method4.pl. This will recursively find and rename all .txt files in the current directory and its subdirectories with the prefix new_.


Method 5: Using opendir and readdir

This method uses the opendir and readdir functions to find and rename files with a prefix. The opendir function opens a directory, and the readdir function reads the contents of the directory. We can use regular expressions to match the filenames and then use the rename function to rename each file with the specified prefix.

#!/usr/bin/perl

use strict;

use warnings;

my $prefix = 'new_';

opendir(my $dh, '.') or die "Can't open current directory: $!";

while (my $file = readdir($dh)) {

    next unless $file =~ /^.*\.txt$/;

    my $new_file = $prefix . $file;

    rename $file, $new_file or warn "Can't rename $file to $new_file: $!";

}

closedir $dh;

Save the script as rename_files_method5.pl and run it with perl rename_files_method5.pl. This will find and rename all .txt files in the current directory with the prefix new_.


Method 6: Using File::Copy

This method uses the File::Copy module to copy files with a prefix to a new directory and then rename the files. The File::Copy module provides functions for copying and moving files. We can use the copy function to copy the original files to a new directory with the prefix, and then use the rename function to rename the files with the specified prefix.

use strict;

use warnings;

use File::Copy;

my $prefix = 'new_';

my $new_dir = 'new_files';

mkdir $new_dir unless -d $new_dir;

opendir(my $dh, '.') or die "Can't open current directory: $!";

while (my $file = readdir($dh)) {

    next unless $file =~ /^.*\.txt$/;

    my $new_file = $prefix . $file;

    copy($file, "$new_dir/$new_file") or warn "Can't copy $file: $!";

}

closedir $dh;

opendir($dh, $new_dir) or die "Can't open $new_dir: $!";

while (my $file = readdir($dh)) {

    next unless $file =~ /^.*\.txt$/;

    my $new_file = $prefix . $file;

    rename("$new_dir/$file", "$new_dir/$new_file") or warn "Can't rename $file: $!";

}

closedir $dh;

Save the script as rename_files_method6.pl and run it with perl rename_files_method6.pl. This will copy all .txt files in the current directory to a new directory named new_files with the prefix new_, and then rename the files with the specified prefix.


Method 7: Using File::Find::Rule

This method uses the File::Find::Rule module to find and rename files with a prefix. The File::Find::Rule module provides a simple interface for finding files that match specified criteria. We can use the name method to match filenames and then use the rename function to rename each file with the specified prefix.

use strict;

use warnings;

use File::Find::Rule;

my $prefix = 'new_';

my @files = File::Find::Rule->file()->name('*.txt')->in('.');

foreach my $file (@files) {

    my $new_file = $prefix . $file;

    rename $file, $new_file or warn "Can't rename $file to $new_file: $!";

}

Save the script as rename_files_method7.pl and run it with perl rename_files_method7.pl. This will find and rename all .txt files in the current directory with the prefix new_.

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Monday 8 June 2020

perl program to copy files from one directory to another directory

Perl script copies all the files with a given extension from one directory to another. The source and destination directories are passed as command-line arguments, along with the file extension.

Method 1:

#!/usr/bin/perl

use File::Copy;

my ($src_dir, $dest_dir, $ext) = @ARGV;

opendir my $dh, $src_dir or die "Couldn't open directory $src_dir: $!";

while (my $filename = readdir $dh) {

    next unless $filename =~ /\.$ext$/; # Match extension

    my $src_path = "$src_dir/$filename";

    my $dest_path = "$dest_dir/$filename";

    copy $src_path, $dest_path or warn "Couldn't copy $filename: $!";

}

closedir $dh;

Save the script as copyfiles.pl and run it with perl copyfiles.pl sourcedir destdir txt. This will copy all the files with the extension "txt" from "sourcedir" to "destdir".

Method 2:Using File::Find

The File::Find module provides a way to recursively traverse a directory tree and perform actions on files that match certain criteria.

#!/usr/bin/perl

use File::Find;

use File::Copy;

my ($source_dir, $dest_dir, $file_ext) = @ARGV;

find(sub {

    return unless -f $_; # Skip directories

    return unless /\.$file_ext$/; # Match file extension

    my $source_file = $File::Find::name;

    $source_file =~ s/^\Q$source_dir\E//; # Remove source directory from path

    my $dest_file = "$dest_dir$source_file";

    mkpath($dest_file); # Create parent directories if necessary

    copy($File::Find::name, $dest_file) or warn "Couldn't copy $File::Find::name: $!";

}, $source_dir);

Save the script as copy_files_method2.pl and run it with perl copy_files_method2.pl /path/to/source/dir /path/to/dest/dir txt. This will copy all files with the extension "txt" from the source directory to the destination directory and preserve the directory structure.

Method 3: Using system()

The system() function in Perl allows you to execute shell commands. You can use the cp command to copy files from one directory to another.

#!/usr/bin/perl

my ($source_dir, $dest_dir, $file_ext) = @ARGV;

my $command = "cp $source_dir/*.$file_ext $dest_dir/";

system($command) == 0 or die "Couldn't execute command: $command";

Save the script as copy_files_method3.pl and run it with perl copy_files_method3.pl /path/to/source/dir /path/to/dest/dir txt. This will copy all files with the extension "txt" from the source directory to the destination directory using the cp command.

Method 4: Using opendir() and readdir()

This method uses the opendir() and readdir() functions to read the contents of a directory and then copy the files matching the specified file extension.

#!/usr/bin/perl

use File::Copy;

my ($source_dir, $dest_dir, $file_ext) = @ARGV;

opendir(DIR, $source_dir) or die "Can't open $source_dir: $!";

my @files = readdir(DIR);

closedir(DIR);

foreach my $file (@files) {

    next unless $file =~ /\.$file_ext$/; # Match file extension

    my $source_file = "$source_dir/$file";

    my $dest_file = "$dest_dir/$file";

    copy($source_file, $dest_file) or warn "Couldn't copy $file: $!";

}

Save the script as copy_files_method4.pl and run it with perl copy_files_method4.pl /path/to/source/dir /path/to/dest/dir txt. This will copy all files with the extension "txt" from the source directory to the destination directory.

Method 5: Using glob()

The glob() function returns a list of filenames that match a specified pattern. You can use this function to get a list of files matching the specified file extension and then copy them to the destination directory.

#!/usr/bin/perl

use File::Copy;

my ($source_dir, $dest_dir, $file_ext) = @ARGV;

foreach my $file (glob("$source_dir/*.$file_ext")) {

    my $dest_file = "$dest_dir/" . (split /\//, $file)[-1];

    copy($file, $dest_file) or warn "Couldn't copy $file: $!";

}

Save the script as copy_files_method5.pl and run it with perl copy_files_method5.pl /path/to/source/dir /path/to/dest/dir txt. This will copy all files with the extension "txt" from the source directory to the destination directory.

Method 6: Using Path::Tiny

The Path::Tiny module provides a simple interface to manipulate file and directory paths. It also provides a copy() function that can be used to copy files from one directory to another.

#!/usr/bin/perl

use Path::Tiny;

my ($source_dir, $dest_dir, $file_ext) = @ARGV;

foreach my $file (path($source_dir)->children(qr/\.${file_ext}$/)) {

    my $dest_file = path($dest_dir, $file->basename);

    $file->copy($dest_file) or warn "Couldn't copy $file: $!";

}

Save the script as copy_files_method6.pl and run it with perl copy_files_method6.pl /path/to/source/dir /path/to/dest/dir txt. This will copy all files with the extension "txt" from the source directory to the destination directory.

The Path::Tiny module also provides other useful functions for working with files and directories, such as move(), rename(), and unlink(). It's worth exploring if you need to do more complex file manipulation in your Perl scripts.

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Wednesday 13 March 2024

The Git & Github Bootcamp Part1 - Master on essentials and the tricky bits: rebasing, squashing, stashing, reflogs, blobs, trees, & more!


Installation & Setup

1. Installing Git: Terminal Vs. GUIs

  • Terminal: A text-based interface to run commands directly on your computer.
  • GUIs (Graphical User Interfaces): Software applications with graphical elements, like buttons and icons, making it easier to perform Git operations without memorizing commands.

2. WINDOWS Git Installation

  • Step 1: Visit git-scm.com and download the Windows version of Git.
  • Step 2: Open the downloaded file and follow the installation instructions. Leave the default settings unless you have a specific need to change them.

3. MAC Git Installation

  • Step 1: Open the Terminal.
  • Step 2: Type git --version and press Enter. If Git is not already installed, this will prompt you to install it.
  • Alternatively, you can use Homebrew by typing brew install git if you have Homebrew installed.

4. Configuring Your Git Name & Email

Before you start using Git, you need to introduce yourself to Git by configuring your user name and email address. This information is important because every Git commit uses this information.

  • Command:
    git config --global user.name "Your Name"
    git config --global user.email "your.email@example.com"
    

5. Installing GitKraken (Our GUI)

GitKraken is a graphical Git client that makes Git commands more user-friendly.

  • Step 1: Go to gitkraken.com and download GitKraken.
  • Step 2: Run the installer and follow the setup instructions.

6. Terminal Crash Course: Creating Files & Folders

Creating files and folders from the terminal is a basic but essential skill.

  • Creating a Folder: Use the mkdir command followed by the name of the folder. For example, mkdir MyProject creates a new folder named MyProject.
  • Creating a File: Use the touch command followed by the filename. For example, touch README.md creates a new file named README.md.

7. Terminal Crash Course: Deleting Files & Folders

Sometimes, you need to clean up or remove unnecessary files and folders.

  • Deleting a File: Use the rm command followed by the filename. For example, rm README.md deletes the README.md file.
  • Deleting a Folder: Use the rm -r command followed by the folder name to remove a folder and its contents. For example, rm -r MyProject deletes the MyProject folder and everything inside it.

Putting It All Together: Creating a New Sample Project

Now that you have Git and GitKraken installed, and you know how to manage files and folders from the terminal, let’s start a new sample project.

  1. Open the Terminal or Git Bash on Windows.
  2. Navigate to where you want to create your project using the cd command (e.g., cd Documents).
  3. Create a new folder for your project (e.g., mkdir SampleProject).
  4. Navigate into your project folder (e.g., cd SampleProject).
  5. Initialize a new Git repository:
    • Command: git init
    • This command creates a new Git repository in your project folder. You’ll see a message like “Initialized empty Git repository in [your project path]/.git/”.
  6. Create your first file (e.g., touch README.md) and open it with a text editor to add some content, such as “This is my first Git project!”.
  7. Add your file to the staging area with Git:
    • Command: git add README.md
    • This command tells Git to start tracking changes to the README.md file.
  8. Commit your changes:
    • Command: git commit -m "Initial commit"
    • This command saves your changes to the repository with a message describing what you did.

Very Basics of Git: Adding & Committing

10. What Is A Git Repo?

A Git repository (repo) is a folder on your computer where Git tracks the changes to your project files. It allows you to save different versions of your project, so you can recall specific versions later. The repository was initialized in your project folder when you ran git init.

11. Our First Commands: git init and git status

  • git init: This command was used to initialize your project folder as a Git repository. It allows Git to start tracking changes in the folder.
  • git status: Use this command to see which changes Git has noticed but not yet recorded. Let’s try it:
    cd SampleProject
    git status
    
    This command will show the status of your repository, including any files that have been added, modified, or are untracked.

12. The Mysterious .git Folder

When you initialize a Git repository, Git creates a hidden folder named .git in your project directory. This folder contains all the information necessary for version control, including logs, configurations, and the status of each file. You typically won’t need to interact with this folder directly.

13. A Common Early Git Mistake

A frequent mistake beginners make is forgetting to stage changes before committing them. Git requires you to “add” changes to the staging area before you can “commit” them to your repository’s history. This two-step process gives you control over exactly what changes you include in a commit.

14. Staging Changes With git add

  • Example: Suppose you’ve edited the README.md file to add more project details. To prepare these changes for a commit, you use the git add command.
    git add README.md
    
  • This command moves the changes in README.md to the staging area, making them ready to be committed.

15. The git log Command (And More Committing)

  • git log: Shows a history of all commits in the repository. Each commit is displayed with its unique ID, the author’s name and email, the date, and the commit message.
    git log
    
  • After staging your changes with git add, commit them with a message describing what you did:
    git commit -m "Updated README with more project details."
    

16. Committing Exercise

Let’s practice adding and committing with a new file:

  1. Create a new file: touch notes.txt
  2. Add some content to notes.txt (use a text editor).
  3. Stage the file: git add notes.txt
  4. Commit the changes with a message: git commit -m "Added notes.txt with project notes."
  5. Check the log: git log

By performing these steps, you’ve practiced adding a new file to your repository, staging it, and committing it with a descriptive message. Remember, git status is a helpful command to use throughout this process to see what changes are staged, unstaged, or untracked.

Expanding on our example project, “SampleProject,” let’s explore commits in detail, focusing on best practices, tools, and techniques to manage your project efficiently.

Commits in Detail

1. Commit Messages: Present Or Past Tense?

Commit messages should be written in the imperative mood, as if giving a command or instruction. This convention matches the messages generated by Git itself for automated commits.

  • Example: Instead of writing “Added feature X,” write “Add feature X.”

2. Escaping VIM & Configuring Git’s Default Editor

When you commit without specifying a message directly in the command line (git commit without -m "message"), Git opens the default text editor (often VIM) to write a commit message. Exiting VIM can be confusing for new users:

  • To exit VIM after adding your commit message, press Esc, type :wq (write and quit), and press Enter.
  • To change the default editor to something you’re more comfortable with (like Nano, which is simpler), run:
    git config --global core.editor "nano"
    
    Now, when you run git commit, Nano will open instead of VIM.

3. A Closer Look At The Git Log Command

git log provides a history of commits. To see more than just the commit hash, author, date, and message, you can use:

  • git log --stat: Shows the number of changes (additions and deletions) per file.
  • git log --pretty=oneline: Shows each commit on a single line, making it easier to read through many commits.
  • git log --graph: Displays a text-based graph of the commit history, useful for visualizing branch merges.

4. Committing With A GUI

Git GUI clients like GitKraken can make committing changes more intuitive for those uncomfortable with the command line. Using our project as an example:

  • Open GitKraken and navigate to your “SampleProject” repository.
  • You’ll see uncommitted changes in a panel or section often labeled “Unstaged Files.”
  • Drag the files you want to commit from “Unstaged” to “Staged.”
  • Write your commit message in the provided field and click the “Commit” button.

5. Fixing Mistakes With Amend

If you make a mistake in your last commit (e.g., forgot to add a file or made a typo in the commit message), you can correct it with git commit --amend. This combines your changes with the previous commit instead of creating a new one.

  • Make the necessary changes or add any missed files.
  • Stage the changes: git add .
  • Amend the commit: git commit --amend -m "New commit message"

6. Ignoring Files w/ .gitignore

Sometimes, there are files or directories you don’t want Git to track (e.g., temporary files, build folders). You can create a .gitignore file in your repository’s root directory and list the patterns for files to ignore.

  • Create a .gitignore file: touch .gitignore
  • Open .gitignore in a text editor and add patterns for files to ignore. For example:
    # Ignore all log files
    *.log
    
    # Ignore the node_modules directory
    node_modules/
    
  • Add and commit the .gitignore file:
    git add .gitignore
    git commit -m "Add .gitignore file"
    

By understanding these detailed aspects of committing in Git, you can maintain a clean, efficient workflow for your projects.

Read more »

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Sunday 12 January 2020

Top 10 examples of grep command in UNIX and Linux

The grep command is a powerful tool for searching and filtering text files in UNIX and Linux systems. It allows users to search for a specific pattern in a file or a set of files and display the lines that match that pattern. This command is incredibly versatile and can be used for a variety of tasks, including log analysis, system administration, and programming.

In this blog post, we'll explore 10 examples of the grep command in UNIX and Linux, with code examples to illustrate each use case. By the end of this post, you'll have a better understanding of how to use this command and how it can help you in your day-to-day tasks.

Example 1: Basic Search

The most basic use case for the grep command is to search for a specific pattern in a file. To do this, simply enter the following command:

The most basic use case for the grep command is to search for a specific pattern in a file. To do this, simply enter the following command:

grep apple fruits.txt

For example, to search for the word "apple" in the file "fruits.txt", enter the following command:

This will display all lines in the file that contain the word "apple".

Example 2: Case-Insensitive Search

By default, the grep command is case-sensitive, which means that it will only match patterns that are identical in case to the search term. However, you can use the -i option to perform a case-insensitive search. For example:

grep -i apple fruits.txt


This will match lines that contain "apple", "Apple", or "APPLE".

Example 3: Search Multiple Files

You can also use the grep command to search multiple files at once. To do this, simply specify the filenames separated by spaces. For example:

grep apple fruits.txt vegetables.txt


This will search for the word "apple" in both the "fruits.txt" and "vegetables.txt" files.

Example 4: Search All Files in a Directory

To search all files in a directory, you can use the wildcard character "*". For example:

grep apple *


This will search for the word "apple" in all files in the current directory.

Example 5: Inverse Search

By default, the grep command displays all lines that match the search pattern. However, you can use the -v option to display all lines that do not match the pattern. For example:

grep -v apple fruits.txt


This will display all lines in the "fruits.txt" file that do not contain the word "apple".

Example 6: Search for Whole Words Only

By default, the grep command will match any occurrence of the search pattern, even if it's part of a larger word. For example, the search term "the" will match words like "there", "theme", and "other". To search for whole words only, use the -w option. For example:

grep -w the story.txt


This will only match the word "the", and not words that contain it as a substring.

Example 7: Recursive Search

If you want to search for a pattern in all files in a directory and its subdirectories, use the -r option. For example:

grep -r apple /home/user/documents


This will search for the word "apple" in all files in the "documents" directory and its subdirectories.

Example 8: Count Matches

If you just want to know how many times a pattern appears in a file, use the -c option. For example:

grep -c apple fruits.txt


Example 9:  Do not Matches

Search for lines that do not contain the word "example" in a file "file.txt"

grep -v "example" file.txt



Example 10: Exclude Matches in File

Search for a word "example" in all files except those with a ".txt" extension

grep "example" --exclude=*.txt *


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Monday 26 July 2021

6 ways to download entire S3 bucket Complete Guide

Amazon Simple Storage Service (S3) is a popular cloud storage solution provided by Amazon Web Services (AWS). It allows users to store and retrieve large amounts of data securely and efficiently. While you can download individual files using the AWS Management Console, there are times when you need to download the entire contents of an S3 bucket. In this guide, we will explore six different methods to accomplish this task, providing step-by-step instructions and code examples for each approach.

Before we begin, you should have the following in place:

  1. An AWS account with access to the S3 service.
  2. AWS CLI installed on your local machine (for CLI methods).
  3. Basic knowledge of the AWS Management Console and AWS CLI.

Method 1: Using the AWS Management Console

Step 1: Log in to your AWS Management Console.
Step 2: Navigate to the S3 service and locate the bucket you want to download.
Step 3: Click on the bucket to view its contents.
Step 4: Select all the files and folders you want to download.
Step 5: Click the "Download" button to download the selected files to your local machine.

Method 2: Using AWS CLI (Command Line Interface)

To download an entire S3 bucket using the AWS CLI, follow these steps:

Step 1: Install the AWS CLI
If you don't have the AWS CLI installed on your local machine, you can download and install it from the official AWS Command Line Interface website: https://aws.amazon.com/cli/

Step 2: Configure AWS CLI with Credentials
Once the AWS CLI is installed, you need to configure it with your AWS credentials. Open a terminal or command prompt and run the following command:

aws configure

You will be prompted to enter your AWS Access Key ID, Secret Access Key, Default region name, and Default output format. These credentials will be used by the AWS CLI to authenticate and access your AWS resources, including the S3 bucket.

Step 3: Download the Entire S3 Bucket
Now that the AWS CLI is configured, you can use it to download the entire S3 bucket. There are multiple ways to achieve this:

Method 1: Using aws s3 sync Command

The sync command is used to synchronize the contents of a local directory with an S3 bucket. To download the entire S3 bucket to your local machine, create an empty directory and run the following command:

aws s3 sync s3://your-bucket-name /path/to/local/directory

Replace your-bucket-name with the name of your S3 bucket, and /path/to/local/directory with the path to the local directory where you want to download the files.

Method 2: Using aws s3 cp Command with --recursive Flag

The cp command is used to copy files between your local file system and S3. By using the --recursive flag, you can recursively copy the entire contents of the S3 bucket to your local machine:

aws s3 cp s3://your-bucket-name /path/to/local/directory --recursive

Replace your-bucket-name with the name of your S3 bucket, and /path/to/local/directory with the path to the local directory where you want to download the files.

Both methods will download all the files and directories from the S3 bucket to your local machine. If the bucket contains a large amount of data, the download process may take some time to complete.

It's important to note that the AWS CLI methods can only be used to download publicly accessible S3 buckets or S3 buckets for which you have appropriate IAM permissions to read objects. If the bucket is private and you don't have the necessary permissions, you won't be able to download its contents using the AWS CLI. In such cases, you may need to use other methods like SDKs or AWS Management Console, as described in the previous sections of this guide.

Method 3: Using AWS SDKs (Software Development Kits)

Step 1: Choose the AWS SDK for your preferred programming language (e.g., Python, Java, JavaScript).
Step 2: Install and configure the SDK in your development environment.
Step 3: Use the SDK's API to list all objects in the bucket and download them one by one or in parallel.

Python Example:

import boto3

# Initialize the S3 client
s3 = boto3.client('s3')

# List all objects in the bucket
bucket_name = 'your-bucket-name'
response = s3.list_objects_v2(Bucket=bucket_name)

# Download each object
for obj in response['Contents']:
    s3.download_file(bucket_name, obj['Key'], obj['Key'])

Method 4: Using AWS DataSync

AWS DataSync is a managed data transfer service that simplifies and accelerates moving large amounts of data between on-premises storage and AWS storage services. To use AWS DataSync to download an entire S3 bucket, follow these steps:

Step 1: Set up a DataSync Task

1.Log in to your AWS Management Console and navigate to the AWS DataSync service.
2.Click on "Create task" to create a new data transfer task.
3.Select "S3" as the source location and choose the S3 bucket you want to download from.
4.Select the destination location where you want to transfer the data, which could be another AWS storage service or an on-premises location.
5.Configure the transfer options, including how to handle file conflicts and transfer speed settings.
6.Review the task settings and click "Create task" to start the data transfer.

Method 5: Using AWS Transfer Family

AWS Transfer Family is a fully managed service that allows you to set up an SFTP, FTP, or FTPS server in AWS to enable secure file transfers to and from your S3 bucket. To download the files using AWS Transfer Family, follow these steps:

Step 1: Set up an AWS Transfer Family Server

  1. Go to the AWS Transfer Family service in the AWS Management Console.
  2. Click on "Create server" to create a new server.
  3. Choose the protocol you want to use (SFTP, FTP, or FTPS) and configure the server settings.
  4. Select the IAM role that grants permissions to access the S3 bucket.
  5. Set up user accounts or use your existing IAM users for authentication.
  6. Review the server configuration and click "Create server" to set up the server.

Step 2: Download Files from the Server

Use an SFTP, FTP, or FTPS client to connect to the server using the server endpoint and login credentials.
Once connected, navigate to the S3 bucket on the server and download the files to your local machine.

Method 6: Using Third-Party Tools

There are various third-party tools available that support downloading S3 buckets. These tools often offer additional features and capabilities beyond the standard AWS options. Some popular third-party tools for S3 bucket downloads include:

Cyberduck: Cyberduck is a free and open-source SFTP, FTP, and cloud storage browser for macOS and Windows. It supports S3 bucket access and provides an intuitive interface for file transfers.

S3 Browser: S3 Browser is a freeware Windows client for managing AWS S3 buckets. It allows you to easily download files from S3 using a user-friendly interface.

Rclone: Rclone is a command-line program to manage cloud storage services, including AWS S3. It offers advanced features for syncing and copying data between different storage providers.

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Wednesday 9 February 2022

Perl - secure web services using Logging and monitoring

Logging and monitoring are critical components of any secure web service. By keeping detailed logs of all activity and monitoring those logs for suspicious activity, we can detect and respond to security threats in a timely manner.

Here's an example code snippet that demonstrates how to implement logging and monitoring in Perl web services using the Log::Log4perl module:

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