sed

Overview

The sed (Stream Editor) command is used to perform basic text transformations on an input stream. It’s a powerful tool for parsing and transforming text using regular expressions.

Syntax

sed [options] 'command' [input-file]

Common Options

Option	Description
-n	Suppress output
-e script	Add script
-f file	Add script file
-i	Edit files in place
-r	Extended regex
-E	Extended regex
-s	Separate files
-l N	Line length
--debug	Debug info
--help	Show help
--version	Show version

Common Commands

Command	Description
p	Print line
d	Delete line
s/pat/rep/	Substitute
y/pat/rep/	Transform chars
i	Insert text
a	Append text
c	Change line
q	Quit
r file	Read file
w file	Write to file

Key Use Cases

1. Text substitution
2. Line filtering
3. Text transformation
4. File editing
5. Data extraction

Examples with Explanations

Example 1: Basic Substitution

sed 's/old/new/' file

Replace first occurrence

Example 2: Global Substitution

sed 's/old/new/g' file

Replace all occurrences

Example 3: Delete Lines

sed '/pattern/d' file

Delete matching lines

Common Usage Patterns

1. Multiple commands:

   sed -e 's/a/b/' -e 's/x/y/'

2. In-place edit:

   sed -i 's/old/new/g' file

3. Line range:

   sed '1,5s/old/new/' file

Security Considerations

1. File permissions
2. Backup files
3. Regular expressions
4. Input validation
5. Command injection

Related Commands

• awk - Pattern scanning
• grep - Pattern matching
• tr - Character translation
• cut - Select fields
• perl - Perl language

Additional Resources

• Sed Manual
• Usage Guide
• Text Processing

Best Practices

1. Test commands
2. Use backups
3. Quote patterns
4. Document changes
5. Verify results

Regular Expressions

1. Basic regex
2. Extended regex
3. Back references
4. Character classes
5. Anchors

Troubleshooting

1. Pattern matching
2. File permissions
3. Backup issues
4. Syntax errors
5. Line endings