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Sed Command Cheatsheet

Table of Contents

Basic Syntax

Terminal window
sed [options] 'command' file
sed [options] -e 'command1' -e 'command2' file
sed [options] -f script-file file
  • options: Modify sed behavior
  • command: Operation to perform
  • file: Input file (optional, can use stdin)

Address Types

Terminal window
sed '1d'           # First line
sed '$d'           # Last line
sed '1,3d'         # Lines 1-3
sed '2,+4d'        # Line 2 and next 4 lines
sed '1~2d'         # Every odd line
sed '2~2d'         # Every even line

Basic Commands

Terminal window
p     # Print line
d     # Delete line
q     # Quit sed
n     # Print line and read next
a     # Append text
i     # Insert text
c     # Change/replace line
=     # Print line number
l     # Print line unambiguously

Text Replacement

Terminal window
# Basic syntax
s/pattern/replacement/[flags]


# Common flags
g     # Global (all occurrences)
1-9   # Nth occurrence only
p     # Print if substitution made
w     # Write to file if substitution made
I     # Case insensitive

Advanced Commands

Hold Space Operations

Terminal window
h     # Copy pattern space to hold space
H     # Append pattern space to hold space
g     # Copy hold space to pattern space
G     # Append hold space to pattern space
x     # Exchange pattern and hold spaces

Flow Control

Terminal window
:label           # Define label
b label          # Branch to label
t label          # Branch on substitute
T label          # Branch if no substitute

Regular Expressions

Terminal window
.     # Any single character
^     # Start of line
$     # End of line
*     # Zero or more occurrences
\+    # One or more occurrences
\?    # Zero or one occurrence
[]    # Character class
[^]   # Negated character class

Multiple Commands

Using Multiple Commands

Terminal window
# Using semicolons
sed 's/old/new/g; s/next/prev/g' file.txt


# Using -e option
sed -e 's/old/new/g' -e 's/next/prev/g' file.txt


# Using a script file
sed -f commands.sed file.txt

File Operations

Terminal window
# In-place editing
sed -i 's/old/new/g' file.txt


# Backup original file
sed -i.bak 's/old/new/g' file.txt


# Write specific lines to file
sed -n '/pattern/w output.txt' file.txt

Practical Examples

Text Processing

Terminal window
# Remove empty lines
sed '/^$/d' file.txt


# Remove comments and empty lines
sed -e '/^#/d' -e '/^$/d' file.txt


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


# Double space output
sed G file.txt

Configuration File Editing

Terminal window
# Change configuration value
sed -i 's/^SETTING=.*/SETTING=newvalue/' config.txt


# Comment out lines
sed -i 's/^[^#]/# &/' file.txt


# Uncomment lines
sed -i 's/^# //' file.txt

Advanced Text Manipulation

Terminal window
# Reverse line order
sed -n '1!G;h;$p' file.txt


# Remove trailing whitespace
sed 's/[[:space:]]*$//' file.txt


# Convert DOS to Unix
sed 's/\r$//' file.txt

Advanced Techniques

Using Labels and Branches

Terminal window
# Conditional processing
sed ':start
     /pattern/ {
         s/old/new/
         t start
     }' file.txt


# Skip blocks of text
sed '/start/,/end/b' file.txt

Using Hold Space

Terminal window
# Reverse paragraphs
sed -e '/./{H;$!d;}' -e 'x;/^\n/d' file.txt


# Duplicate lines
sed 'h;p' file.txt


# Swap lines
sed 'N;s/\(.*\)\n\(.*\)/\2\n\1/' file.txt

Tips and Best Practices

  1. Debugging

    Terminal window
    # Print commands as executed
    sed -n 'l' file.txt
    

    # Use echo for testing
    echo "test" | sed 's/test/working/'

  2. Performance

    Terminal window
    # Use -E for complex patterns
    sed -E 's/(complex|pattern)/simple/g'
    

    # Combine multiple operations
    sed 's/one/1/g; s/two/2/g'

  3. Safety

    Terminal window
    # Make backups
    sed -i.bak 's/old/new/g' file.txt
    

    # Test commands before running
    sed -n 's/pattern/replacement/gp' file.txt