bash
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Strict mode with safe IFS
Fail fast on errors, unset vars, pipe failures; split only on newline/tab
set -euo pipefail; IFS=$'\n\t'
Cleanup temp dir via trap
Auto-remove mktemp dir on exit/signal; note: quote $tmp to survive spaces
tmp=$(mktemp -d); trap 'rm -rf "$tmp"' EXIT INT TERM
Diff two command outputs
Process substitution compares two streams without temp files
diff <(kubectl get cm a -o yaml) <(kubectl get cm b -o yaml)
Read file lines into array safely
mapfile -t strips newlines; handles spaces unlike for-loop word splitting
mapfile -t lines < file.txt; printf '%s\n' "${lines[@]}"
Parameter expansion toolkit
basename, strip extension, and global replace without spawning sed/basename
f=/var/log/app.log.gz; echo "${f##*/}" "${f%.*}" "${f//log/LOG}"
Regex capture with BASH_REMATCH
Native regex match extracts groups; note: don't quote the right-hand regex
[[ $s =~ ^([0-9]+)\.([0-9]+) ]] && echo "${BASH_REMATCH[1]}/${BASH_REMATCH[2]}"
Parallel xargs over null-delimited input
Run N parallel jobs safely with NUL separators for names with spaces
find . -name '*.log' -print0 | xargs -0 -P"$(nproc)" -n1 gzip
Check PIPESTATUS of each stage
Inspect exit code of every pipe stage; $? only reports the last command
curl -s "$url" | jq .data; echo "${PIPESTATUS[@]}"
getopts flag parsing
POSIX option parsing with arguments; -n takes a value, -v is a switch
while getopts "n:v" o; do case $o in n) ns=$OPTARG;; v) verbose=1;; esac; done
Bound command with timeout and kill
SIGTERM at 30s then SIGKILL after 5s grace; exit 124 means it was killed
timeout -k 5s 30s ./long_task.sh || echo "timed out: $?"
Dedicated fd for structured logging
Open fd 3 to a file, write to it independently of stdout, then close it
exec 3>>audit.log; echo "$(date -Is) start" >&3; exec 3>&-
zsh recursive glob and batch rename
zsh: list only regular files recursively, then mass-rename safely with zmv
setopt extendedglob; print -l **/*(.); autoload zmv; zmv '(*).txt' '$1.bak'
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