Text Processing

Code

# grep, cut, paste
grep -E "ERROR|WARN" app.log
grep -v "^#" /etc/ssh/sshd_config | grep -v "^$"
cut -d: -f1 /etc/passwd
paste -d, names.txt ages.txt

# awk for column processing
awk -F: '$3 >= 1000 {print $1}' /etc/passwd
awk '{sum += $1} END {print sum}' numbers.txt

# sed for in-place editing
sed -i 's/old/new/g' config.txt
sed -n '10,20p' file.txt

# sort, uniq, head
sort access.log | uniq -c | sort -rn | head -20

# jq for JSON
curl -s https://api.github.com/repos/cli/cli | jq '.stargazers_count'

Explanation

grep filters lines, cut extracts fields, and awk processes columns with full programming power for sums and conditions. sed performs stream edits, with -i for in-place file changes. Combining sort, uniq -c, and sort -rn produces frequency rankings, and jq queries JSON like sed for text.

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