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File system commands provide tools for navigating, creating, modifying, and managing files and directories in the virtual filesystem.

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Directory Listing

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ls

List directory contents with various formatting options. Usage: ls [options] [path...] Options:
  • -l - Long format with permissions, size, and date
  • -a - Show hidden files (starting with .)
  • -1 - One entry per line
Examples: 
# List current directory
ls

# Long format with details
ls -l

# Show all files including hidden
ls -la

# List specific directory
ls /home/user/documents
Output example: 
$ ls -l
-rw-r--r--  1 user user   1234 Jan 15 10:30 file.txt
drwxr-xr-x  1 user user    512 Jan 14 09:15 docs
-rwxr-xr-x  1 user user   4096 Jan 16 14:22 script.sh

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File Content

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cat

Concatenate and display file contents. Usage: cat [file...] Examples: 
# Display file content
cat file.txt

# Concatenate multiple files
cat file1.txt file2.txt

# Read from stdin (for piping)
echo "hello" | cat
Output the first part of files. Usage: head [options] [file...] Options:
  • -n NUM - Output first NUM lines (default: 10)
Examples: 
# First 10 lines
head file.txt

# First 5 lines
head -n 5 file.txt

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tail

Output the last part of files. Usage: tail [options] [file...] Options:
  • -n NUM - Output last NUM lines (default: 10)
Examples: 
# Last 10 lines
tail file.txt

# Last 20 lines
tail -n 20 file.txt

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File Operations

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cp

Copy files and directories. Usage: cp [options] source dest Options:
  • -r - Copy directories recursively
Examples: 
# Copy file
cp file.txt backup.txt

# Copy directory recursively
cp -r mydir mydir_backup

# Copy to different location
cp file.txt /home/user/documents/

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mv

Move or rename files and directories. Usage: mv source dest Examples: 
# Rename file
mv oldname.txt newname.txt

# Move file to directory
mv file.txt /home/user/documents/

# Move directory
mv mydir /home/user/newlocation/

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rm

Remove files and directories. Usage: rm [options] file... Options:
  • -r - Remove directories recursively
  • -f - Force removal without prompting
Examples: 
# Remove file
rm file.txt

# Remove directory and contents
rm -r mydir

# Force remove multiple files
rm -rf temp1 temp2 temp3

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touch

Create empty files or update timestamps. Usage: touch file... Examples: 
# Create empty file
touch newfile.txt

# Create multiple files
touch file1.txt file2.txt file3.txt

# Update timestamp of existing file
touch existing.txt

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Directory Operations

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mkdir

Create directories. Usage: mkdir [options] directory... Options:
  • -p - Create parent directories as needed
Examples: 
# Create directory
mkdir mydir

# Create nested directories
mkdir -p parent/child/grandchild

# Create multiple directories
mkdir dir1 dir2 dir3

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rmdir

Remove empty directories. Usage: rmdir directory... Examples: 
# Remove empty directory
rmdir emptydir

# Remove multiple empty directories
rmdir dir1 dir2 dir3

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find

Search for files in directory hierarchy. Usage: find [path] [options] Options:
  • -name pattern - Match filename pattern
  • -type f|d - Match files (f) or directories (d)
  • -maxdepth N - Limit search depth
Examples: 
# Find all .txt files
find . -name "*.txt"

# Find directories only
find /home -type d

# Find files with depth limit
find . -maxdepth 2 -name "*.js"

# Combine filters
find . -type f -name "test*.js"
Output example: 
$ find . -name "*.md"
./README.md
./docs/guide.md
./docs/api.md

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tree

Display directory tree structure. Usage: tree [options] [path] Options:
  • -L N - Limit depth to N levels
  • -d - Show directories only
Examples: 
# Show full tree
tree

# Limit to 2 levels
tree -L 2

# Directories only
tree -d
Output example: 
$ tree -L 2
.
├── README.md
├── src
│   ├── index.js
│   └── utils
└── package.json

2 directories, 3 files

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File Information

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stat

Display file status information. Usage: stat file... Examples: 
# Show file stats
stat file.txt

# Multiple files
stat file1.txt file2.txt

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file

Determine file type. Usage: file file... Examples: 
# Identify file type
file document.pdf
file script.sh
file image.png

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du

Estimate file space usage. Usage: du [options] [path...] Options:
  • -h - Human-readable sizes
  • -s - Display only total for each argument
Examples: 
# Disk usage of current directory
du

# Human-readable format
du -h

# Total size only
du -sh /home/user/documents

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df

Report filesystem disk space usage. Usage: df [options] Examples: 
# Show filesystem usage
df

# Human-readable format
df -h

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Permissions

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chmod

Change file permissions. Usage: chmod [options] mode file... Options:
  • -R - Change files and directories recursively
Mode formats:
  • Octal: 644, 755, 777
  • Symbolic: u+x, g-w, o=r, a+x
Examples: 
# Octal mode
chmod 755 script.sh
chmod 644 document.txt

# Add execute permission
chmod +x script.sh

# Remove write for group
chmod g-w file.txt

# Set exact permissions for user
chmod u=rwx,g=rx,o=r file.txt

# Recursive
chmod -R 755 mydir/

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chown

Change file owner and group. Usage: chown [options] owner[:group] file... Options:
  • -R - Change files and directories recursively
Examples: 
# Change owner
chown user file.txt

# Change owner and group
chown user:group file.txt

# Recursive
chown -R user:group mydir/

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Path Utilities

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basename

Strip directory from filename. Usage: basename path [suffix] Examples: 
# Extract filename
basename /home/user/file.txt
# Output: file.txt

# Remove suffix
basename /home/user/file.txt .txt
# Output: file

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dirname

Extract directory from path. Usage: dirname path Examples: 
# Extract directory
dirname /home/user/file.txt
# Output: /home/user

# Current directory
dirname file.txt
# Output: .

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realpath

Print resolved absolute path. Usage: realpath path... Examples: 
# Get absolute path
realpath ../documents/file.txt

# Resolve symlinks
realpath link-to-file

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ln

Create links between files. Usage: ln [options] target link Options:
  • -s - Create symbolic link
Examples: 
# Create hard link
ln file.txt hardlink.txt

# Create symbolic link
ln -s /path/to/file.txt symlink.txt

# Link directory
ln -s /home/user/docs documents

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Temporary Files

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mktemp

Create temporary file or directory. Usage: mktemp [options] [template] Options:
  • -d - Create directory instead of file
Examples: 
# Create temp file
mktemp
# Output: /tmp/tmp.xyz123

# Create temp directory
mktemp -d
# Output: /tmp/tmp.abc456

# Custom template
mktemp myfile.XXXXXX

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Common Patterns

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Backup files

cp important.txt important.txt.bak

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Find and remove

find . -name "*.tmp" -type f | xargs rm

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Directory size report

du -sh */ | sort -h

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Count files by extension

find . -type f | sed 's/.*\.//' | sort | uniq -c

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