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File Operations

Directory Navigation​

# Change directory
cd /path/to/directory
cd ~                    # Home directory
cd -                    # Previous directory
cd ..                   # Parent directory
cd ../..                # Two levels up

# Print working directory
pwd
pwd -P                  # Physical path (resolve symlinks)

# Directory stack
pushd /path/to/dir      # Push directory onto stack
popd                    # Pop directory from stack
dirs                    # Show directory stack

Listing Files​

# Basic listing
ls
ls -l                   # Long format
ls -la                  # Include hidden files
ls -lh                  # Human-readable sizes
ls -lt                  # Sort by modification time
ls -lS                  # Sort by file size

# Recursive listing
ls -R
find . -type f          # All files recursively
find . -type d          # All directories recursively

# Tree view (if available)
tree
tree -a                 # Include hidden files
tree -d                 # Directories only
tree -L 2               # Limit depth to 2

File and Directory Operations​

Creating Files and Directories​

# Create empty file
touch file.txt
touch file1.txt file2.txt    # Multiple files

# Create directory
mkdir directory
mkdir -p path/to/nested/dir  # Create parent directories

# Create file with content
echo "Hello World" > file.txt
cat > file.txt << EOF
Line 1
Line 2
EOF

# Create temporary files
mktemp                  # Create temporary file
mktemp -d               # Create temporary directory
mktemp -t prefix.XXXXXX # Create with template

Copying Files​

# Copy file
cp source.txt dest.txt
cp source.txt /path/to/dest/

# Copy directory
cp -r source_dir dest_dir

# Copy with options
cp -i source dest       # Interactive (prompt before overwrite)
cp -u source dest       # Update (copy only if source is newer)
cp -v source dest       # Verbose
cp -p source dest       # Preserve attributes

# Copy multiple files
cp file1.txt file2.txt dest_dir/
cp *.txt dest_dir/

# Backup while copying
cp file.txt{,.bak}      # Creates file.txt.bak

Moving and Renaming​

# Move/rename file
mv oldname.txt newname.txt
mv file.txt /path/to/new/location/

# Move directory
mv old_dir new_dir

# Move with options
mv -i source dest       # Interactive
mv -u source dest       # Update only
mv -v source dest       # Verbose

# Rename multiple files
for file in *.txt; do
    mv "$file" "${file%.txt}.backup"
done

Removing Files​

# Remove file
rm file.txt
rm -f file.txt          # Force removal
rm -i file.txt          # Interactive

# Remove directory
rmdir empty_dir         # Remove empty directory
rm -r directory         # Remove directory and contents
rm -rf directory        # Force remove directory

# Safe removal with confirmation
rm -i *.txt

# Remove files older than N days
find . -name "*.log" -mtime +7 -delete

File Permissions​

Understanding Permissions​

# View permissions
ls -l file.txt
# Output: -rw-r--r-- 1 user group 1024 Jan 1 12:00 file.txt
#         ||||||||| |  |    |     |    |   |  |   |
#         |owner|group|other|links|user|group|size|date|name
#         |rwx |rwx |rwx |

# Permission bits
r = read (4)
w = write (2)
x = execute (1)

Changing Permissions​

# Chmod with symbolic notation
chmod u+x file.txt      # Add execute for user
chmod g-w file.txt      # Remove write for group
chmod o=r file.txt      # Set other to read only
chmod a+r file.txt      # Add read for all

# Chmod with octal notation
chmod 755 file.txt      # rwxr-xr-x
chmod 644 file.txt      # rw-r--r--
chmod 600 file.txt      # rw-------

# Recursive permissions
chmod -R 755 directory/

# Common permission patterns
chmod 755 script.sh     # Executable script
chmod 644 document.txt  # Regular file
chmod 600 private.key   # Private key
chmod 700 ~/.ssh/       # SSH directory

Changing Ownership​

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

# Recursive ownership
chown -R user:group directory/

# Change group only
chgrp group file.txt

# Copy ownership from another file
chown --reference=ref_file target_file

File Information​

File Statistics​

# File information
stat file.txt
file file.txt           # File type
du -h file.txt          # Disk usage
wc -l file.txt          # Line count
wc -w file.txt          # Word count
wc -c file.txt          # Character count

# Directory size
du -sh directory/       # Human-readable directory size
du -h --max-depth=1     # Size of subdirectories

File Attributes​

# Extended attributes (Linux)
getfattr -d file.txt
setfattr -n user.comment -v "My comment" file.txt

# Immutable attribute (Linux)
chattr +i file.txt      # Make immutable
chattr -i file.txt      # Remove immutable
lsattr file.txt         # List attributes

Finding Files​

Find Command​

# Basic find
find . -name "*.txt"
find /path -name "filename"

# Find by type
find . -type f          # Files only
find . -type d          # Directories only
find . -type l          # Symbolic links only

# Find by size
find . -size +100M      # Larger than 100MB
find . -size -1k        # Smaller than 1KB
find . -size 500c       # Exactly 500 bytes

# Find by time
find . -mtime -7        # Modified in last 7 days
find . -atime +30       # Accessed more than 30 days ago
find . -ctime -1        # Changed in last 24 hours

# Find by permissions
find . -perm 644        # Exactly 644
find . -perm -644       # At least 644
find . -perm /644       # Any of 644 bits set

# Execute commands on found files
find . -name "*.txt" -exec cat {} \;
find . -name "*.log" -exec rm {} \;
find . -name "*.tmp" -delete

Locate Command​

# Update locate database
updatedb

# Find files quickly
locate filename
locate "*.txt"

# Case-insensitive search
locate -i filename

Which and Whereis​

# Find executable in PATH
which command
which -a command        # All matches

# Find command, source, and manual
whereis command
# Create symbolic link
ln -s /path/to/target linkname
ln -s ../file.txt symlink.txt

# Create relative symbolic link
ln -sr target linkname

# Read symbolic link
readlink linkname
readlink -f linkname    # Follow all links

# Find broken links
find . -type l -! -exec test -e {} \; -print
# Create hard link
ln target hardlink

# Find hard links
find . -samefile original_file
find . -inum $(stat -c %i original_file)

# Count hard links
ls -l file.txt          # Second column shows link count

Archive Operations​

Tar Archives​

# Create tar archive
tar -cf archive.tar file1 file2 directory/
tar -czf archive.tar.gz directory/     # With gzip compression
tar -cjf archive.tar.bz2 directory/    # With bzip2 compression

# Extract tar archive
tar -xf archive.tar
tar -xzf archive.tar.gz
tar -xjf archive.tar.bz2

# List archive contents
tar -tf archive.tar
tar -tzf archive.tar.gz

# Extract specific files
tar -xf archive.tar file1 file2

# Add files to existing archive
tar -rf archive.tar newfile.txt

Compression​

# Gzip compression
gzip file.txt           # Creates file.txt.gz
gunzip file.txt.gz      # Extracts file.txt
gzip -k file.txt        # Keep original file

# Bzip2 compression
bzip2 file.txt          # Creates file.txt.bz2
bunzip2 file.txt.bz2    # Extracts file.txt

# Zip archives
zip -r archive.zip directory/
unzip archive.zip
unzip -l archive.zip    # List contents

File Monitoring​

Watching Files​

# Monitor file changes
tail -f /var/log/syslog
tail -f -n 100 logfile.txt    # Last 100 lines

# Watch command output
watch -n 2 'ls -la'     # Run command every 2 seconds
watch -d 'df -h'        # Highlight differences

# Monitor file modifications
inotifywait -m /path/to/file    # Requires inotify-tools

File Comparison​

# Compare files
diff file1.txt file2.txt
diff -u file1.txt file2.txt     # Unified format
diff -c file1.txt file2.txt     # Context format

# Compare directories
diff -r dir1/ dir2/

# Other comparison tools
cmp file1.txt file2.txt         # Binary comparison
comm file1.txt file2.txt        # Line-by-line comparison

Advanced File Operations​

File Descriptors​

# Redirect to file descriptor
exec 3> output.txt
echo "Hello" >&3
exec 3>&-               # Close file descriptor

# Read from file descriptor
exec 4< input.txt
read -u 4 line
exec 4<&-               # Close file descriptor

Process Substitution​

# Use command output as file
diff <(ls dir1) <(ls dir2)
while read line; do
    echo "Line: $line"
done < <(find . -name "*.txt")

File Locking​

# Exclusive lock
flock -x /tmp/lockfile command
flock -n /tmp/lockfile command    # Non-blocking

# Shared lock
flock -s /tmp/lockfile command

# Lock file descriptor
exec 200>/tmp/lockfile
flock -n 200 || exit 1

Best Practices​

Safety Practices​

# Always quote file paths
cp "$source" "$destination"

# Check if file exists before operations
if [ -f "$file" ]; then
    cp "$file" "$backup"
fi

# Use absolute paths for important operations
cp /full/path/to/source /full/path/to/dest

# Create backups before destructive operations
cp important_file{,.bak}

Performance Tips​

# Use find instead of ls for large directories
find . -maxdepth 1 -name "*.txt"

# Avoid unnecessary file operations
# Bad: cat file | grep pattern
# Good: grep pattern file

# Use appropriate tools for file size
# Large files: use head/tail instead of loading entire file
head -n 100 large_file.txt