GNU Coreutils Quick Reference Guide

A practical reference guide for commonly used GNU utilities with examples and explanations.

Visit the GNU Coreutils Manual

Common Option Patterns

File Operations

ls (List Directory Contents)

List files and directories with various options.

# Basic usage
ls              # List contents
ls -l           # Long format
ls -a           # Include hidden files
ls -lh          # Human-readable sizes
ls -R           # Recursive listing
ls -lt          # Sort by modification time

# Common combinations
ls -lah         # Long format, human-readable, including hidden
ls -ltr         # Long format, sorted by time, reverse order

# Examples
ls /etc         # List contents of /etc
ls -l *.txt     # List all text files in long format

cp (Copy)

Copy files and directories.

# Basic usage
cp file1 file2          # Copy file1 to file2
cp -r dir1 dir2         # Copy directory recursively
cp -p file1 file2       # Preserve permissions
cp -i file1 file2       # Interactive (prompt before overwrite)

# Advanced usage
cp -al                  # Hard link files instead of copying
cp -u file1 file2       # Copy only when source is newer

mv (Move)

Move or rename files and directories.

# Basic usage
mv file1 file2          # Rename file1 to file2
mv file1 dir1           # Move file1 to dir1
mv -i file1 file2       # Interactive mode
mv -n file1 file2       # No overwrite

# Examples
mv *.txt dir1           # Move all text files to dir1
mv -v file1 file2       # Verbose output

rm (Remove)

Remove files and directories.

# Basic usage
rm file1                # Remove file
rm -r dir1              # Remove directory recursively
rm -f file1             # Force removal (no prompt)
rm -i file1             # Interactive mode

# Safe practices
rm -I *.txt             # Prompt once before removing multiple files
rm -rf dir1/*           # Remove directory contents (be careful!)

mkdir (Make Directory)

Create directories.

# Basic usage
mkdir dir1              # Create directory
mkdir -p path/to/dir    # Create parent directories as needed
mkdir -m 755 dir1       # Create with specific permissions

# Examples
mkdir dir1 dir2 dir3    # Create multiple directories
mkdir -pv path/to/dir   # Verbose output with parent creation

chmod (Change Mode)

Change file permissions.

# Basic usage
chmod 755 file1         # Set specific permissions
chmod u+x file1         # Add execute permission for user
chmod go-w file1        # Remove write permission for group/others

# Recursive changes
chmod -R 755 dir1       # Change permissions recursively
chmod -R u+X dir1       # Add execute for directories only

# Common settings
chmod 644 file1         # Standard file permissions (rw-r--r--)
chmod 755 script.sh     # Standard executable permissions (rwxr-xr-x)

chown (Change Owner)

Change file owner and group.

# Basic usage
chown user file1                # Change owner
chown user:group file1          # Change owner and group
chown -R user:group dir1        # Recursive change

# Examples
chown -R www-data:www-data /var/www  # Web server files
chown --reference=file1 file2        # Copy ownership

Text Processing

cat (Concatenate)

View and combine files.

# Basic usage
cat file1               # Display file contents
cat file1 file2         # Concatenate files
cat -n file1            # Show line numbers
cat -A file1            # Show all characters

# Creating files
cat > file1             # Create new file (Ctrl+D to end)
cat >> file1            # Append to file

less (View File Contents)

View files with scrolling and search.

# Basic usage
less file1              # View file
less -N file1           # Show line numbers
less +F file1           # Follow file (like tail -f)

# Navigation
/pattern                # Search forward
?pattern                # Search backward
n                       # Next search result
N                       # Previous search result
g                       # Go to start
G                       # Go to end

head (View Beginning)

View the start of files.

# Basic usage
head file1              # Show first 10 lines
head -n 20 file1        # Show first 20 lines
head -c 100 file1       # Show first 100 bytes

# Multiple files
head -n 1 *.txt         # First line of each text file

tail (View End)

View the end of files.

# Basic usage
tail file1              # Show last 10 lines
tail -n 20 file1        # Show last 20 lines
tail -f file1           # Follow file in real time
tail -f -n0 file1       # Follow file from end

# Multiple files
tail -n 1 *.log         # Last line of each log file

grep (Search Text)

Search text using patterns.

# Basic usage
grep pattern file1              # Search for pattern
grep -i pattern file1           # Case-insensitive search
grep -r pattern dir1            # Recursive search
grep -v pattern file1           # Invert match

# Advanced usage
grep -E 'pattern1|pattern2'     # Extended regex
grep -w word file1              # Match whole words
grep -l pattern files           # List matching files
grep -c pattern file1           # Count matches

sed (Stream Editor)

Edit text streams.

# Basic usage
sed 's/old/new/' file1          # Replace first occurrence
sed 's/old/new/g' file1         # Replace all occurrences
sed -i 's/old/new/g' file1      # Edit file in place

# Advanced usage
sed '1d' file1                  # Delete first line
sed '/pattern/d' file1          # Delete matching lines
sed 's/.*pattern.*/new/' file1  # Replace entire line

awk (Text Processing)

Process and analyze text files.

# Basic usage
awk '{print $1}' file1          # Print first field
awk -F: '{print $1}' file1      # Use custom delimiter
awk 'NR>1' file1                # Skip first line

# Advanced usage
awk '{sum+=$1} END {print sum}' # Sum first column
awk '$1 > 100'                  # Filter rows
awk '{printf "%-10s %s\n", $1, $2}'  # Formatted output

System Information

ps (Process Status)

Display process information.

# Basic usage
ps                      # Show user processes
ps aux                  # Show all processes
ps -ef                  # Full format listing

# Common uses
ps aux | grep process   # Find specific process
ps -u username          # Show user's processes
ps --sort=-%cpu        # Sort by CPU usage

top (System Monitor)

Monitor system processes in real-time.

# Basic usage
top                     # Start top
top -u username         # Show user's processes

# Interactive commands
k                       # Kill process
r                       # Renice process
f                       # Select fields to display
q                       # Quit

df (Disk Free)

Show disk space usage.

# Basic usage
df                      # Show disk usage
df -h                   # Human-readable sizes
df -T                   # Show filesystem type
df -i                   # Show inode information

# Examples
df -h /home             # Check specific partition
df --total             # Show total

du (Disk Usage)

Show directory space usage.

# Basic usage
du                      # Show usage
du -h                   # Human-readable sizes
du -s                   # Summary only
du -sh *                # Usage of all items in current directory

# Examples
du -sh /var/log/*       # Check log sizes
du -h --max-depth=1    # Show one level deep

Network Utilities

ping (Network Connectivity)

Test network connectivity.

# Basic usage
ping host              # Ping continuously
ping -c 4 host         # Send 4 packets
ping -i 2 host         # 2 second interval

# Examples
ping -w 5 host         # 5 second timeout
ping -s 1000 host      # Use 1000 byte packets

curl (Transfer Data)

Transfer data from or to a server.

# Basic usage
curl url               # Get content
curl -o file url       # Save to file
curl -O url           # Save with remote filename

# Advanced usage
curl -H "Header" url  # Custom header
curl -X POST url      # POST request
curl -d "data" url    # Send data

wget (Download Files)

Download files from web.

# Basic usage
wget url              # Download file
wget -O file url      # Save with different name
wget -c url           # Continue download

# Advanced usage
wget -r url           # Recursive download
wget --limit-rate=100k url  # Limit bandwidth
wget -b url           # Background download

Archive Utilities

tar (Tape Archive)

Create and extract archives.

# Create archives
tar -cvf archive.tar files    # Create archive
tar -czvf archive.tar.gz files  # Create compressed archive
tar -cjvf archive.tar.bz2 files # Create bz2 archive

# Extract archives
tar -xvf archive.tar         # Extract
tar -xzvf archive.tar.gz     # Extract gzip
tar -xjvf archive.tar.bz2    # Extract bz2

# View contents
tar -tvf archive.tar         # List contents

gzip (Compression)

Compress or expand files.

# Basic usage
gzip file              # Compress file
gzip -d file.gz        # Decompress
gzip -l file.gz        # List contents

# Advanced usage
gzip -r directory      # Compress directory
gzip -9 file           # Maximum compression
gzip -k file           # Keep original file

Best Practices

  1. Use man pages for detailed help

    man command

  2. Check command options

    command --help

  3. Test destructive commands first

    rm -i file          # Interactive mode
mv -i file dest     # Prompt before overwrite

  4. Use verbose mode when learning

    cp -v file dest
rm -v file

Further Resources