🧾 sed Command Cheatsheet (Stream Editor)

sed is a powerful Unix utility for parsing and transforming text using stream editing.

📌 Basic Syntax

sed [OPTIONS] 'script' [file...]

• 'script': One or more editing commands.
• [file]: Input file(s). If omitted, sed reads from standard input.

⚙️ Common Options

✂️ Basic Commands

🔍 Substitution Syntax

sed 's/pattern/replacement/flags' file

Flags

Examples

sed 's/foo/bar/' file       # Replace first 'foo' with 'bar'
sed 's/foo/bar/g' file      # Replace all 'foo' with 'bar'
sed 's/foo/bar/2' file      # Replace second 'foo' only
sed 's/foo/bar/ip' file     # Case-insensitive + print

🗑️ Deletion with sed

sed can delete lines based on line numbers, patterns, or ranges.

🔢 Delete by Line Number

sed '2d' file             # Delete line 2
sed '5,10d' file          # Delete lines 5 through 10

🔍 Delete by Pattern

sed '/error/d' file       # Delete lines containing 'error'
sed '/^$/d' file           # Delete blank lines
sed '/^#/d' file           # Delete comment lines (starting with #)

🧮 Delete by Range and Pattern

sed '1,/pattern/d' file   # Delete from line 1 to first match of 'pattern'
sed '/start/,/end/d' file # Delete lines between 'start' and 'end' (inclusive)

🧠 Conditional Deletion

sed -n '/pattern/!p' file # Print only lines NOT matching 'pattern'

🧹 Delete Last Line

sed '$d' file             # Delete the last line

📍 Addressing Lines

Line Numbers

sed '2d' file            # Delete line 2
sed '3,5p' file          # Print lines 3 to 5

Patterns

sed '/error/d' file      # Delete lines containing 'error'
sed '/^#/d' file         # Delete comment lines

Combined

sed '1,/pattern/d' file  # Delete from line 1 to first match of 'pattern'

🧪 Advanced Substitution

Using Capture Groups

sed 's/\(foo\)bar/\1baz/' file

• \(...\) captures a group.
• \1, \2, etc., refer to captured groups.

Escaping Special Characters

sed 's/\/usr\/bin/\/usr\/local\/bin/' file

Or use alternate delimiter:

sed 's|/usr/bin|/usr/local/bin|' file

🧨 In-Place Editing

sed -i 's/foo/bar/g' file           # Edit file directly
sed -i.bak 's/foo/bar/g' file       # Backup original as file.bak

📂 Multiple Commands

Inline

sed -e 's/foo/bar/' -e '/baz/d' file

Block Syntax

sed '
s/foo/bar/
s/baz/qux/
' file

🧵 Append, Insert, Change

sed '/pattern/a\Text to append' file
sed '/pattern/i\Text to insert' file
sed '/pattern/c\New line content' file

🔄 Translate Characters

sed 'y/abc/ABC/' file     # a→A, b→B, c→C

🧠 Useful Recipes

Remove Blank Lines

sed '/^$/d' file

Remove Leading/Trailing Whitespace

sed 's/^[ \t]*//' file     # Remove leading
sed 's/[ \t]*$//' file     # Remove trailing

Replace Tabs with Spaces

sed 's/\t/    /g' file

Number Lines

sed = file | sed 'N;s/\n/\t/'

📚 Resources

• man sed
• GNU sed manual: https://www.gnu.org/software/sed/manual/sed.html