Advanced Sed Text Transformation

# Basic substitution
sed 's/old/new/g' file.txt

# Replace only on specific lines
sed '5,10s/old/new/g' file.txt        # Lines 5-10
sed '/pattern/s/old/new/g' file.txt   # Lines containing pattern

# Multiple replacements
sed -e 's/old/new/g' -e 's/foo/bar/g' file.txt
sed 's/old/new/g; s/foo/bar/g' file.txt

# Use different delimiter
sed 's|/usr/bin|/usr/local/bin|g' file.txt
sed 's#/old/path#/new/path#g' file.txt

# Backreferences
sed 's/\(word\)/\U\1/' file.txt            # Uppercase first word
sed 's/\(.*\):\(.*\)/\2:\1/' file.txt    # Swap columns

# Case conversion
sed 's/.*/\L&/' file.txt      # Entire line to lowercase
sed 's/.*/\U&/' file.txt      # Entire line to uppercase
sed 's/\b\(.\)/\U\1/g' file.txt  # Title case words

# Delete operations
sed '/pattern/d' file.txt                      # Delete matching lines
sed '/start/,/end/d' file.txt                  # Delete range
sed '5,10d' file.txt                           # Delete lines 5-10

# Insert/append text
sed '3i\New line before line 3' file.txt      # Insert before
sed '3a\New line after line 3' file.txt       # Append after
sed '/pattern/a\New line' file.txt            # Append after pattern

# Change entire line
sed '/pattern/c\Replacement line' file.txt
sed '5c\New line 5' file.txt

# Print specific lines
sed -n '10,20p' file.txt                       # Print lines 10-20
sed -n '/start/,/end/p' file.txt               # Print range
sed -n '/pattern/p' file.txt                   # Print matching lines

# In-place editing (with backup)
sed -i.bak 's/old/new/g' file.txt
sed -i '' 's/old/new/g' file.txt               # macOS (no backup)

# Read from another file
sed '/pattern/r otherfile.txt' file.txt

# Write to another file
sed '/pattern/w output.txt' file.txt

# Hold space operations (advanced)
sed '1!G;h;$!d' file.txt                       # Reverse file
sed -n 'G; s/\n/&&/; /^\n\n/d; s/\n//; h; P' file.txt  # Uniq adjacent

# Number lines
sed = file.txt | sed 'N;s/\n/\t/'            # Add line numbers

# Join lines
sed ':a;N;$!ba;s/\n/ /g' file.txt             # All lines to one
sed 'N;s/\n/ /' file.txt                      # Join pairs

# Conditional branching
sed '/pattern/{n;s/old/new/;}' file.txt        # Next line after pattern
sed '/start/,/end/{s/old/new/g;}' file.txt     # Only in range

# Multi-line patterns
sed '/first/{N;/first\nsecond/s/old/new/;}' file.txt

# Address with regex
sed '/^#/d' file.txt                           # Delete comment lines
sed '/^$/d' file.txt                           # Delete empty lines
sed '/^[[:space:]]*$/d' file.txt               # Delete blank lines

# Transform specific columns
sed 's/\([^,]*\),\{0,1\}/\U\1,/g' file.csv  # Uppercase first column