Linux 106: Working with Files and Directories

Welcome to the next installment of our Linux series! In this article, we’ll cover essential concepts and commands for working with files and directories on Linux. Files and directories are the backbone of any operating system, and understanding how to manage them efficiently will make your Linux experience much smoother.

From creating and managing files to handling permissions and symbolic links, this article will guide you through everything you need to know to work effectively with files and directories on Linux.

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1. File System Structure

Before diving into commands, it's helpful to understand the layout of the Linux file system. Here's an overview of some key directories:

• / (Root): The top-level directory containing the entire file system.
• /home/: User directories (e.g., /home/user).
• /etc/: System configuration files.
• /var/: Variable files such as logs and temporary data.
• /tmp/: Temporary files that are often cleared on reboot.
• /usr/: User programs and libraries.
• /bin/: Essential system binaries.

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2. Navigating the File System

Using pwd to Print the Current Directory

The pwd (print working directory) command shows you the path of the directory you're currently in.

pwd

Example output:

/home/user/Documents

Changing Directories with cd

The cd (change directory) command allows you to navigate the file system.

• To go to a specific directory:

cd /path/to/directory

• To go up one directory level:

cd ..

• To return to your home directory:

cd ~

• To go back to the previous directory:

cd -

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3. Creating and Deleting Files

Creating Files

You can create a new file with commands like touch and echo.

• Using touch:

touch newfile.txt

This creates an empty file named newfile.txt.

• Using echo:

echo "Hello, world!" > file.txt

This creates a file named file.txt and writes "Hello, world!" into it.

Deleting Files

To delete a file, use the rm command.

• Remove a single file:

rm file.txt

• Remove a directory (empty):

rmdir directory_name

• Remove a directory and its contents recursively:

rm -r directory_name

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4. Working with Directories

Creating Directories

You can create new directories using the mkdir command.

mkdir new_directory

If you need to create parent directories that don't exist, use the -p option.

mkdir -p /path/to/new_directory

Listing Files and Directories

To list files and directories in the current directory, use the ls command.

• Basic listing:

ls

• Long listing with additional details:

bash

ls -l

• Listing including hidden files:

ls -a

• Listing files with specific file type (e.g., directories):

ls -d */

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5. Copying and Moving Files

Copying Files

The cp command allows you to copy files or directories.

• Copy a file:

bash

cp source_file destination_file

• Copy a directory recursively:

bash

cp -r source_directory destination_directory

Moving Files

The mv command is used for both moving and renaming files or directories.

• Move a file:

bash

mv source_file destination_file

• Rename a file:

bash

mv oldname.txt newname.txt

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6. Working with File Permissions

Linux uses file permissions to control who can read, write, and execute files. Each file and directory has three types of permissions for three different user categories:

• Owner: The user who owns the file.
• Group: The group associated with the file.
• Others: Everyone else.

Viewing Permissions with ls -l

bash

ls -l

Example output:

sql

-rwxr-xr-x 1 user group 12345 Apr 10 14:32 script.sh

In this example:

• rwx (read, write, execute) for the owner.
• r-x (read, execute) for the group.
• r-x (read, execute) for others.

Changing Permissions with chmod

Use the chmod command to change file permissions.

• Give execute permission to the owner:

bash

chmod u+x file.sh

• Remove read permission for others:

bash

chmod o-r file.txt

• Set specific permissions (e.g., rwx for owner, r-x for group, and no permissions for others):

bash

chmod 750 file.txt

Changing Ownership with chown

The chown command allows you to change the owner and/or group of a file or directory.

bash

chown user:group file.txt

This changes the owner of file.txt to user and the group to group.

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7. Symbolic Links

A symbolic link (or symlink) is a pointer to another file or directory. It’s like a shortcut, allowing you to access the target file or directory from a different location.

Creating a Symbolic Link

To create a symbolic link, use the ln -s command:

bash

ln -s /path/to/target /path/to/link

For example, to create a symlink named my_link pointing to my_file.txt:

bash

ln -s my_file.txt my_link

Removing Symbolic Links

To remove a symbolic link, use the rm command:

bash

rm my_link

Note that rm does not remove the target file, only the symlink.

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8. Searching for Files and Directories

Finding Files with find

The find command allows you to search for files and directories in a specific location.

• Find a file by name:

bash

find /path/to/search -name "filename"

• Find files by type:

bash

find /path/to/search -type f    # Find files
find /path/to/search -type d    # Find directories

Using locate for Faster Search

If your system uses the locate database (which is updated regularly), you can quickly search for files by name.

bash

locate filename

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9. Archiving and Compressing Files

Creating a Tar Archive

Use the tar command to create an archive of files and directories.

bash

tar -cvf archive.tar /path/to/files

Extracting a Tar Archive

bash

tar -xvf archive.tar

Compressing Files

You can also compress files using gzip or bzip2:

• Using gzip:

bash

gzip file.txt

• Using bzip2:

bash

bzip2 file.txt

To extract these compressed files, use gunzip for gzip files and bunzip2 for bzip2 files.

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Wrapping Up

Working with files and directories is an essential skill for any Linux user. In this article, we covered how to navigate the file system, create, copy, move, and delete files, and manage file permissions. Additionally, we explored symbolic links, searching for files, and archiving.

Next Steps:

• Learn about file system mounting and how to manage storage devices.
• Explore advanced file permission techniques and Access Control Lists (ACLs).
• Dive deeper into file system management tools like df, du, and fsck.

In the next article, “Linux 107: File System Management and Mounting”, we’ll take a closer look at file system management and mounting storage devices.