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Master sed for text transformation and substitution. Part of the Unix text processing trinity (grep, sed, awk). Learn to replace patterns globally, convert file formats (CSV to TSV), remove debug messages, and clean datasets efficiently. Essential for data processing pipelines!

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At-a-glance checklist

• [ ] Understand sed's role in the trinity: grep (find), sed (substitute), awk (process)
• [ ] Master basic substitution syntax: sed 's/pattern/replacement/'
• [ ] Use /g flag for global replacement (all occurrences on each line)
• [ ] Apply /gi flags for global case-insensitive replacement
• [ ] Delete lines matching patterns with sed '/pattern/d'
• [ ] Convert CSV to TSV by replacing commas with tabs: sed 's/,/\t/g'
• [ ] Remove debug statements from log files with delete commands
• [ ] Understand time complexity: bubble sort O(n²) vs quicksort O(n log n)
• [ ] Pipe sed output to gnuplot for data visualization
• [ ] Transfer files between systems using scp (secure copy)
• [ ] Build complete pipelines: generate → clean with sed → plot

Key takeaways

sed transforms text: While grep finds patterns, sed changes them. One command can clean thousands of lines instantly.

Global flag matters: sed 's/,/;/' replaces first comma only. sed 's/,/;/g' replaces all commas on each line. Always check if you need /g!

Delete is powerful: sed '/pattern/d' removes entire lines. Perfect for stripping debug output, comments, or unwanted data from logs.

Complete workflows: Generate data → clean with sed → visualize with gnuplot → transfer with scp. Unix tools chain together for end-to-end data processing without Excel!