Linux File Management

I’m learning DevOps and Linux, and I want to share my notes about working with files and folders. I keep things simple because I’m still learning.

What You’ll Learn

How the Linux file system works
How to move around folders
How to create, copy, move, and delete files
How to use paths and wildcards
How to read and search file contents
How to use grep to find text
How to compare files
How to work with file editors

1. The Linux File System

In Linux, everything starts from the root folder /. It is like C:\ in Windows, but Linux does not use drive letters.

Example structure:

/
├── home/
│   ├── reza/
│   └── john/
├── etc/
├── var/
└── usr/

Important folders to remember: • /home → user folders like /home/reza • /root → admin user’s home folder (need sudo) • /etc → configuration and system files • /var → logs and temporary data • /usr → programs and libraries • /tmp → temporary files (deleted after restart)

2. Moving Around

pwd → shows where I am now

pwd

ls → lists files and folders

ls
ls -l     # long format
ls -a     # show hidden files

cd → move to another folder

cd Documents
cd ..      # go up one level
cd ~       # go to my home folder

3. Understanding Paths

Absolute path starts from /:

cd /home/reza/Documents

Relative path starts from where I am:

cd Documents
cd ../john

Special symbols to remember:

. → current folder
.. → one level up
~ → my home folder

4. Creating Files and Folders

mkdir → create a new folder

The -p option stands for parents. It tells Linux to automatically create all missing folders in the path.

mkdir my_folder
mkdir -p projects/web/react

touch → create an empty file

touch file.txt

Add text to a file:

echo "Hello World" > file.txt
echo "More text" >> file.txt

5. Copying Files

cp → copy files

cp file.txt backup.txt
cp file.txt ~/Documents/

Copy folders (use -r for recursive):

cp -r folder1 folder2

6. Moving or Renaming

mv → move or rename files

mv oldname.txt newname.txt
mv file.txt Documents/

No need for -r when moving folders.

7. Deleting Files and Folders

rm → delete files

rm file.txt

rm -r → delete folders and everything inside

rm -r folder_name

Be careful, there’s no trash bin. Safe way:

rm -i file.txt

rmdir → removes empty folders only

rmdir empty_folder

8. Reading Files

cat – Show Whole File

The simplest way to see a file:

cat file.txt

Show multiple files:

cat file1.txt file2.txt

Good for: Small files
Bad for: Big files (floods the screen!)
Warning: Never use cat on binary files (images, executables) – it breaks the terminal!

head – Show Beginning

See first 10 lines:

head file.txt

See first 5 lines:

head -n 5 file.txt

When I use this: Checking log files, seeing file headers

tail – Show End

See last 10 lines:

tail file.txt

See last 20 lines:

tail -n 20 file.txt

Watch file live (great for logs!):

tail -f /var/log/syslog

This keeps showing new lines as they’re added. Press Ctrl+C to stop.

When I use this: Watching log files in real-time, checking recent entries

less – View Page by Page

A program to read files page by page. Much better than cat for big files.

less bigfile.txt

Navigation in less:

Space → Next page
b → Previous page
Arrow keys → Move up/down
g → Go to beginning
G → Go to end
q → Quit

Searching in less: Press / then type search term:

# Inside less:
/error        # Find "error"
n            # Next match
N            # Previous match

Why I Use less:

Doesn’t load entire file at once (fast!)
Can search • Can go back and forth •
Doesn’t mess up my terminal

9. Searching in Files with grep

What is grep?

Searches for text patterns in files. Super useful!

grep = Global Regular Expression Print

Basic Usage

grep "search_term" file.txt

Example:

grep "error" logfile.log
# Shows all lines with "error"

Useful grep Options

grep -i "error" file.txt          # Ignore case (Error, ERROR, error)
grep -n "error" file.txt          # Show line numbers
grep -v "error" file.txt          # Show lines WITHOUT "error"
grep -r "error" /var/log/         # Search recursively in folder
grep -l "error" *.log             # Show only filenames with matches
grep -c "error" file.txt          # Count matching lines

Search Multiple Files

grep "error" *.log                # Search all .log files
grep "error" file1.txt file2.txt  # Search specific files

Common Patterns I Use

# Find errors in logs
grep -i "error" /var/log/syslog

# Find my IP address
grep "192.168" /etc/hosts

# Find failed login attempts
grep "Failed password" /var/log/auth.log

# Count errors
grep -c "error" application.log

Advanced grep

Using Regular Expressions:

grep "^error" file.txt        # Lines starting with "error"
grep "error$" file.txt        # Lines ending with "error"
grep "error.*warning" file.txt # Lines with error then warning
grep "[0-9]" file.txt         # Lines with numbers

Grep with Pipes:

ps aux | grep nginx           # Find nginx processes
ls -la | grep "txt"           # Find txt files in listing
cat file.txt | grep "error"   # Same as: grep "error" file.txt

Context Lines:

grep -A 3 "error" file.txt    # Show 3 lines After match
grep -B 2 "error" file.txt    # Show 2 lines Before match
grep -C 2 "error" file.txt    # Show 2 lines of Context (before and after)

10. Wildcards (Working with Many Files at Once)

Wildcards help you work with many files or folders using one command instead of typing each name. They are very useful when you have many files with similar names.

* (Asterisk) – Matches Anything

The star * means “any number of characters.” You can use it anywhere in a file name.

Examples:

ls *.txt
# Shows all files that end with .txt (for example: notes.txt, report.txt, list.txt)

ls file*
# Shows all files that start with "file" (for example: file1.txt, fileA.txt, file_backup.log)

rm *.log
# Deletes all files that end with .log (for example: system.log, app.log, error.log)

cp *.jpg Pictures/
# Copies all image files that end with .jpg into the Pictures folder.

? (Question Mark) – Matches One Character

The question mark ? replaces only one single character.

Examples:

ls file?.txt
# Matches files like: file1.txt, fileA.txt, fileb.txt
# But not: file10.txt (because it has two extra characters)

ls ???.txt
# Matches any file name that has exactly three characters before .txt
# (for example: cat.txt, dog.txt, log.txt)

Practice Tip: You can test your wildcard command with ls first to make sure it matches what you expect. For example:

ls *.txt

Then if it looks correct, you can safely run:

rm *.txt

This helps avoid deleting the wrong files.

11. Finding Files (Search Anywhere in Linux)

When your folders have many files, it’s easy to lose something. The find command helps you search for a file or folder by name, type, or size.

The basic format is:

find [where_to_search] [option] [what_to_find]

For example:

find . -name "file.txt"
# . means start searching in the current folder
# -name "file.txt" means look for a file with this exact name

Common Examples

Find a file in the current folder and subfolders:

find . -name "notes.txt"

Find all .log files inside /home:

find /home -name "*.log"

Find all .txt files (case insensitive):

find . -iname "*.txt"
# -iname ignores upper or lower case (so it matches both FILE.TXT and file.txt)

Find only files (not folders):

find . -type f -name "*.sh"
# -type f means look for regular files.

Find only folders:

find . -type d -name "backup"
# -type d means look for directories (folders).

Advanced Examples

Find large files (more than 10MB):

find . -type f -size +10M
# +10M means larger than 10 megabytes
# You can also use -10M for smaller than 10MB

Find files changed in the last 2 days:

find . -mtime -2
# -mtime checks when the file was last modified
# -2 means in the last two days

Find and delete specific files:

find . -name "*.tmp" -delete
# Deletes all temporary .tmp files under the current folder.
# Use this carefully, it does not ask for confirmation.

Practice Tip: When using find, start with small areas like . (current folder) before searching your whole system. Example:

find . -name "*.log"

is faster and safer than

find / -name "*.log"

which searches the entire computer.

12. Comparing Files

diff – Compare Two Files

See differences between files:

diff file1.txt file2.txt

Output symbols:

< = line from first file
> = line from second file
a = added
d = deleted
c = changed

Side-by-Side View

diff -y file1.txt file2.txt

Ignore Case and Whitespace

diff -i file1.txt file2.txt        # Ignore case
diff -w file1.txt file2.txt        # Ignore whitespace

13. Text Editors in Terminal

nano – Easy Editor

Simple text editor:

nano file.txt

Controls (shown at bottom):

Ctrl+O = Save (Write Out)
Ctrl+X = Exit
Ctrl+K = Cut line
Ctrl+U = Paste
Ctrl+W = Search

I use nano when: Quick edits, simple config changes

vim – Advanced Editor

Powerful but harder to learn:

vim file.txt

Two modes:

Normal mode (default) – for commands
Insert mode – for typing (press i)

Basic vim commands:

i = Enter insert mode
Esc = Back to normal mode
:w = Save
:q = Quit
:wq = Save and quit
:q! = Quit without saving

Quick Comparison

nano: Easy to learn, usually installed, basic features, my choice for quick edits
vim: Hard to learn, always installed, very powerful, my choice for serious work

14. File Analysis Tools

file – Identify File Type

file document.pdf
# Output: PDF document

file image.jpg
# Output: JPEG image data

file script.sh
# Output: Bash script

Useful when file has wrong extension or no extension.

wc – Word Count

wc file.txt
# Output: lines words bytes filename

Count lines only:

wc -l file.txt

Count words only:

wc -w file.txt

Count characters:

wc -m file.txt

Practical Examples

# Count files in directory
ls | wc -l

# Count log entries
grep "error" app.log | wc -l

# Count lines of code
find . -name "*.py" | xargs wc -l

15. Sorting and Unique Lines

sort – Sort Lines

sort file.txt               # Sort alphabetically
sort -r file.txt            # Reverse sort
sort -n file.txt            # Sort numerically
sort -u file.txt            # Sort and remove duplicates

uniq – Remove Duplicate Lines

Important: File must be sorted first!

sort file.txt | uniq        # Remove duplicates
sort file.txt | uniq -c     # Count occurrences
sort file.txt | uniq -d     # Show only duplicates

Practical Example

Find most common errors in log:

grep "error" app.log | sort | uniq -c | sort -rn

This:

Finds all error lines
Sorts them
Counts duplicates
Sorts by count (highest first)

16. File Permissions (Basic Idea)

Example:

-rw-r--r-- 1 reza reza 1234 Oct 19 10:30 file.txt

What it means: • rw- → owner can read and write • r– → group can read only • r– → others can read only

17. Command Quick Reference

Navigation

pwd → Show current folder
ls → List files
cd folder → Go to folder
cd .. → Go up one level
cd ~ → Go home

File Actions

touch file.txt → Create file
mkdir folder → Create folder
cp file1 file2 → Copy file
cp -r dir1 dir2 → Copy folder
mv old new → Move or rename
rm file → Delete file
rm -r folder → Delete folder

Reading Files

cat file.txt → Show whole file
head file.txt → Show first 10 lines
tail file.txt → Show last 10 lines
tail -f file.txt → Watch file live
less file.txt → View file page by page

Searching

grep “text” file → Find text in file
grep -i “text” file → Case insensitive search
grep -r “text” folder/ → Search in folder
grep -n “text” file → Show line numbers
grep -v “text” file → Show lines without text

File Analysis

wc -l file → Count lines
diff file1 file2 → Compare files
file filename → Show file type
sort file → Sort lines
uniq file → Remove duplicates

What I Learned

Everything starts from /
Use pwd, ls, and cd to move around
Use absolute or relative paths
Add -r when copying folders
rm deletes permanently
Wildcards save time
Always check your path before removing files
Use less for large files, cat for small ones
grep is super powerful for searching
tail -f is perfect for watching logs
Always pipe through sort before using uniq
nano for quick edits, vim for power users
Regular expressions make grep even more useful

Common Commands

# Watch logs
tail -f /var/log/nginx/error.log

# Find errors
grep -i "error" /var/log/syslog | less

# Count errors today
grep "$(date +%Y-%m-%d)" /var/log/app.log | grep -c "ERROR"

# Find config files
find /etc -name "*.conf"

# Check file before editing
less /etc/nginx/nginx.conf

# Quick edit
vim ~/.bashrc

# Find large files
find . -type f -size +100M

# Most common errors
grep ERROR app.log | sort | uniq -c | sort -rn | head

# Test wildcard commands safely
ls *.txt

# Find and count specific file types
find . -name "*.py" | wc -l

Tips

Always check your current folder with pwd.
Use rm -i to confirm before deleting.
Test wildcard commands with ls first.
Practice in test folders before using real files.
Keep backups of important data.
Use less instead of cat for large files.
Learn a few grep patterns, they’re incredibly useful.
Start with nano for editing, learn vim later.
When in doubt, check the manual with man command.

That’s my complete guide to Linux file management! Now I can navigate, create, read, search, and manage files.

Linux File Management