File and Directory Management

File Permissions

Every file and directory has permissions for three types of users: - Owner (u) - Group (g) - Others (o)

And three types of permissions: - Read (r) - 4 - Write (w) - 2 - Execute (x) - 1

Viewing Permissions

ls -l

Output format: -rw-r--r-- 1 user group size date filename

• First character: File type (- for file, d for directory)
• Next 9: Permissions (owner-group-others)
• Owner permissions, group permissions, others permissions

Changing Permissions

chmod permissions filename

Methods: 1. Symbolic: chmod u+x filename (add execute to owner) 2. Octal: chmod 755 filename (rwxr-xr-x)

Common permissions: - 644: rw-r--r-- (files) - 755: rwxr-xr-x (executables) - 700: rwx------ (private)

Changing Ownership

sudo chown user:group filename

File Types

• Regular files: -
• Directories: d
• Symbolic links: l
• Character devices: c
• Block devices: b
• Sockets: s
• Named pipes: p

Finding Files

locate

locate filename

Fast search using a database (updated daily by cron).

find

find /path -name "pattern"

Powerful but slower. Examples: - find . -name "*.txt": Find all .txt files in current directory - find /home -type f -size +1M: Find files larger than 1MB - find . -mtime -7: Files modified in last 7 days

which

which command

Find the location of a command in PATH.

whereis

whereis command

Find binary, source, and manual files.

Archiving and Compression

tar

Create archives: bash tar -cvf archive.tar files/ Extract: bash tar -xvf archive.tar

With compression: - gzip: tar -czvf archive.tar.gz files/ - bzip2: tar -cjvf archive.tar.bz2 files/ - xz: tar -cJvf archive.tar.xz files/

zip

zip archive.zip files/
unzip archive.zip

Disk Usage

du

du -h directory

Show disk usage of directories.

df

df -h

Show filesystem disk space usage.

File Comparison

diff

diff file1 file2

Show differences between files.

cmp

cmp file1 file2

Compare files byte by byte.

Text Processing

grep

Search for patterns in files: bash grep "pattern" file grep -r "pattern" directory

sed

Stream editor for text manipulation: bash sed 's/old/new/g' file

awk

Text processing and reporting: bash awk '{print $1}' file

Symbolic Links

Create links: bash ln -s target link_name - Hard links: ln target link_name - Soft links: ln -s target link_name

Practice Exercises

1. Check permissions of files in your home directory.
2. Create a script file and make it executable.
3. Find all .txt files in your system.
4. Create a tar archive of your Documents folder.
5. Compare two text files and see the differences.

Next, we'll explore text editors available in Linux.