Code-Memo

Debugging and optimization

Quick debugging tools

bash -n script.sh (syntax check)
shellcheck script.sh (lint, if installed)
set -x / bash -x script.sh (trace)
set -euo pipefail (fail fast + catch unset vars)

Tracing

bash -x script.sh arg1 arg2

More controlled:

set -x
do_work
set +x

Common issues

Word splitting / globbing: fix with quoting "$var" and "$@"
Unsafe reads: use read -r and IFS=
Pipelines hide errors: use set -o pipefail

Timing / profiling (lightweight)

time ./script.sh

Measure sections:

start="$(date +%s)"
do_work
echo "elapsed=$(( $(date +%s) - start ))s"

Performance tips

Prefer builtins over spawning many processes in loops
Use awk once instead of multiple grep | cut | sed when appropriate
Avoid cat file | ... when the tool accepts a filename directly