Pipes and tools: grep, sed, awk, sort

Chain commands with |, and the text tools available to scripts: grep, sed, awk, sort, uniq, cut, tr, wc.

Runs in Zerethon IDE · Bash 5.2 Official Bash documentation ↗

main.sh

grep -c ERROR log.txt
grep -v INFO log.txt | sort | uniq -c | sort -rn
awk '{ count[$1]++ } END { for (k in count) print k, count[k] }' log.txt | sort
sed 's/disk full/disk is full/' log.txt | head -n 2
cut -d' ' -f1 log.txt | sort -u | paste -sd, -
awk 'BEGIN { printf "%.2f\n", 7 / 2 }'

log.txt

INFO start
ERROR disk full
INFO retry
ERROR disk full
WARN slow

Output

2
      2 ERROR disk full
      1 WARN slow
ERROR 2
INFO 2
WARN 1
INFO start
ERROR disk is full
ERROR,INFO,WARN
3.50

a | b sends the output of a to the input of b.
uniq only merges lines that are next to each other — sort first.
awk splits each line into fields $1, $2…, and does decimal arithmetic, which Bash cannot.
The tools are the BusyBox versions of the Alpine image: the common options work, but a few GNU-only options do not (sed -i on project files would also fail — they are read-only).

Pipes and tools: grep, sed, awk, sort

Related topics

Official references