Text Processing: grep and paste

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Master grep for pattern searching and paste for merging files. Part of the Unix text processing trinity (grep, sed, awk). Learn to process log files, extract CSV columns, count patterns, and create datasets efficiently. Process substitution saves I/O, and always cut first before grepping!

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At-a-glance checklist

• [ ] Understand the trinity: grep (find), sed (substitute), awk (process)
• [ ] Use grep to search for patterns in files and output matching lines
• [ ] Master grep -i for case-insensitive search (crucial for log analysis)
• [ ] Learn anchors: ^ for line start, $ for line end
• [ ] Use paste -d',' to merge files line-by-line and create CSV files
• [ ] Apply process substitution <(command) to avoid temporary files (saves I/O!)
• [ ] Always use cut first to extract specific columns before grepping (avoid false positives)
• [ ] Combine curl with grep to scrape and search web pages
• [ ] Practice with real datasets (NYC Airbnb listings, XML files, log files)
• [ ] Remember: I/O operations are expensive - process substitution is your friend

Key takeaways

grep is everywhere: Log analysis, data filtering, web scraping - essential for any data work. The -i flag alone makes it 10x more useful.

Process substitution: paste -d',' <(grep title file) <(grep author file) beats creating temp files. Faster, cleaner, no cleanup.

Cut first, grep second: Searching entire lines finds "Manhattan" in descriptions. Extract column 5 first, then grep - accurate results guaranteed.

Trinity power: grep finds patterns, sed transforms them, awk processes data. One session per tool - this is just the beginning!