Text Processing

Code

#!/bin/bash

# grep: search text
grep "pattern" file.txt
grep -i "pattern" file.txt  # Ignore case
grep -r "pattern" dir/      # Recursive search
grep -n "pattern" file.txt  # Show line numbers
grep -v "pattern" file.txt  # Invert match
grep -c "pattern" file.txt  # Match count
grep -E "pat1|pat2" file.txt  # Extended regex

# sed: stream editor
sed 's/old/new/' file.txt        # Replace first
sed 's/old/new/g' file.txt       # Global replace
sed -i 's/old/new/g' file.txt    # In-place edit
sed '/pattern/d' file.txt        # Delete matching lines
sed '3d' file.txt                # Delete line 3
sed '2,5d' file.txt              # Delete lines 2-5
sed -n '10,20p' file.txt         # Print lines 10-20

# awk: text analysis
awk '{print $1}' file.txt        # Print column 1
awk -F',' '{print $2}' file.csv  # Specify delimiter
awk 'NR>1' file.txt              # Skip first line
awk '{sum+=$1} END{print sum}' file.txt  # Sum
awk '$3>100' file.txt            # Conditional filter
awk '{print NR, $0}' file.txt    # Add line numbers

# cut: extract field
cut -d',' -f1,3 file.csv  # Extract columns 1,3
cut -c1-10 file.txt       # Extract chars 1-10

# sort & uniq
sort file.txt | uniq          # Deduplicate
sort file.txt | uniq -c       # Count
sort -rn file.txt             # Numeric descending
sort -t',' -k2 file.csv       # Sort by column 2

# tr: character translation
echo "HELLO" | tr 'A-Z' 'a-z'  # To lowercase
cat file.txt | tr -d '\n'      # Delete newlines

Explanation

grep search, sed replace, awk analyze, cut extract, sort/uniq sort and deduplicate are core text processing tools.

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