CLI commands

grep

grep -i "pattern" file

Case-insensitive search.

grep -r "pattern" /path/to/dir

Recursive search through a directory.

grep -v "pattern" file

Invert match — show lines not matching the pattern.

grep -A 3 -B 2 "pattern" file

Show 2 lines before and 3 lines after matching lines.

grep -E "foo|bar" file

Use extended regex to match multiple patterns.

grep -n "pattern" file

Show line numbers where matches occur.

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awk

awk '{print $1}' file

Print the first column.

awk -F ":" '{print $1, $3}' /etc/passwd

Use : as a field separator, print fields 1 and 3.

awk '$3 > 100' file

Only show lines where the third column is greater than 100.

awk '{sum += $2} END {print sum}' file

Calculate the sum of the second column.

awk 'NR % 2 == 0' file

Print every second line (even lines).

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Files

du -sh ./*

Show size of every item in the current directory.

find . -type f -mtime -3

Find files modified in the last 3 days.

find . -name "*.log" -exec rm {} \;

Find and delete all .log files.

sort -k2 -n file

Sort file numerically by the second column.

sort file | uniq -c | sort -nr

Count and rank duplicate lines.

Tidbits

Replace last command

ncim hello.md
^ncim^nvim^

Remove text and square brackets from file names

rename 's/\ \[.*\]//' *