Linux CLI cheat sheet

Search text

• grep — print lines matching a pattern
  • Files: grep "users" /etc/group
  • From another command: ps -ef | grep "root"

Field processing

• awk — select and format fields
  • First field in passwd: awk -F":" '{ print $1 }' /etc/passwd
  • Reorder ls columns: ls -l | awk '{ print $9, $1 }'

Stream edits

• sed — find and replace or delete lines
  • Replace text in a file: sed 's/Unix/UNIX/g' pressRel
  • Replace delimiters in a stream: grep "usr" /etc/passwd | sed 's/:/ /g'
  • Delete first line: ls -1 /tmp | sed '1d'

Counts

• wc — count words, lines, or bytes
  • Words in a file: wc -w verona.txt
  • Lines from a command: who | wc -l

Head and tail

• head — first N lines
  • First 7 lines: head -n 7 /etc/motd
• tail — last N lines
  • Last 5 lines: tail -n 5 build.log
  • Last line from a command: du . | tail -n 1

Sort and unique

• sort — sort lines
  • Sort a file: sort inventory
  • Sort command output: who | sort
• uniq — remove adjacent duplicates (use after sort)
  • Deduplicate a sorted file: uniq sortedRecords
  • Deduplicate who output: who | sort | uniq

Archive and transfer

• tar over SSH — stream archive to a remote host
  • Create on local, extract on remote dir: tar -czf - * | ssh target_user@target_domain tar -xzf - -C target_dir/

Handy combinations

• Top 10 most common log entries: sort access.log | uniq -c | sort -nr | head -n 10