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                   SED COMMAND CHEAT SHEET - QUICK REFERENCE
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SED (Stream EDitor) - powerful text processing utility for filtering and
transforming text.

Basic Syntax:
  sed [options] 'command' file.txt
  command | sed [options] 'command'

COMMON OPTIONS
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  -i[suffix]  Edit files in-place (with optional backup)
  -e          Specify multiple commands
  -f script   Take commands from a file
  -n          Suppress automatic printing of pattern space
  -r, -E      Use extended regular expressions
  
ADDRESSING - SELECTING LINES
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  n           Line number                    sed '2s/foo/bar/' file.txt
  $           Last line                      sed '$s/foo/bar/' file.txt
  n,m         Line range                     sed '2,5s/foo/bar/' file.txt
  n,+m        n and next m lines             sed '2,+3s/foo/bar/' file.txt
  /pat/       Lines matching pattern         sed '/error/s/foo/bar/' file.txt
  /pat/,/pat/ Range between patterns         sed '/start/,/end/s/foo/bar/' file.txt
  addr!       All except matching lines      sed '/error/!s/foo/bar/' file.txt

BASIC TEXT OPERATIONS
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  s/old/new/          Replace first occurrence     sed 's/error/warning/' file.txt
  s/old/new/g         Replace all occurrences      sed 's/error/warning/g' file.txt
  s/old/new/gi        Case-insensitive replace     sed 's/Error/warning/gi' file.txt
  s/old/new/2         Replace 2nd occurrence       sed 's/error/warning/2' file.txt
  s/old/new/2g        Replace 2nd & subsequent     sed 's/error/warning/2g' file.txt
  s|old|new|g         Alternative delimiters       sed 's|/var/log|/opt/log|g' file.txt

LINE OPERATIONS
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  d           Delete lines                   sed '/error/d' file.txt
  5d          Delete specific line           sed '5d' file.txt
  5,10d       Delete line range              sed '5,10d' file.txt
  /pat/d      Delete matching lines          sed '/DEBUG/d' file.txt
  p           Print lines                    sed -n '/ERROR/p' file.txt
  a\text      Append after line              sed '/pattern/a\New line' file.txt
  i\text      Insert before line             sed '/pattern/i\New line' file.txt
  c\text      Change/replace entire line     sed '/pattern/c\Replacement' file.txt

ADVANCED OPERATIONS
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  s/(.+)/\1/  Capture groups (basic regex)   sed 's/\(user\) \(name\)/\2, \1/' file.txt
  s/(.+)/\1/  Capture groups (extended)      sed -E 's/(user) (name)/\2, \1/' file.txt
  &           Reuse matched pattern          sed 's/user/[&]/' file.txt
  =           Print line number              sed = file.txt
  N           Append next line to pattern    sed 'N; s/\n/ /' file.txt
  P           Print first part until \n      sed 'N; P; D' file.txt
  D           Delete first part until \n     sed 'N; P; D' file.txt
  h           Copy pattern to hold space     sed 'h; s/a/A/g; H; g' file.txt
  H           Append pattern to hold space   sed 'h; s/a/A/g; H; g' file.txt
  g           Get hold space, copy to pat.   sed 'h; s/a/A/g; H; g' file.txt
  G           Get hold space, append to pat. sed 'G' file.txt

MULTIPLE OPERATIONS
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  cmd1; cmd2  Execute multiple commands      sed 's/old/new/g; s/foo/bar/g' file.txt
  {cmds}      Group commands                 sed '/match/{s/old/new/g; d}' file.txt

COMMON PRACTICAL EXAMPLES
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  • Remove empty lines:
    sed '/^$/d' file.txt

  • Remove leading whitespace:
    sed 's/^[ \t]*//' file.txt

  • Remove trailing whitespace:
    sed 's/[ \t]*$//' file.txt

  • Convert DOS/Windows to Unix line endings:
    sed 's/\r$//' file.txt

  • Remove comments:
    sed 's/#.*$//' file.txt

  • Extract lines between two patterns (inclusive):
    sed -n '/START_PATTERN/,/END_PATTERN/p' file.txt

  • Number each line:
    sed = file.txt | sed 'N;s/\n/\t/'

  • Replace in multiple files:
    sed -i 's/old/new/g' *.txt

  • Add text at beginning of file:
    sed '1i\# This is a header' file.txt

  • Add text at end of file:
    sed '$a\# This is a footer' file.txt

  • Replace only on specific section:
    sed '/START/,/END/{s/foo/bar/g}' file.txt

SPECIAL CHARACTERS (NEED ESCAPING)
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  \   /   .   *   [   ]   ^   $   &

COMMON REGEX PATTERNS
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  .           Any single character
  *           Zero or more of previous character
  .*          Zero or more of any character
  \+          One or more of previous character (extended regex)
  \?          Zero or one of previous character (extended regex)
  ^           Start of line
  $           End of line
  [abc]       Any character in the set
  [^abc]      Any character not in the set
  [a-z]       Any character in the range
  \1, \2      Back-references to capture groups

TIPS AND BEST PRACTICES
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  • Test without -i first to preview changes
  • Always create backups with -i.bak for important files
  • Use different delimiters (|, :, #) when pattern contains /
  • For complex operations, consider writing a sed script file
  • Chain simple operations instead of writing complex ones
  • Use extended regex (-E) for cleaner syntax with capturing groups

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