linux-bash-scripting

# Linux Bash Scripting Target: GNU Bash 4.4+ on Linux. No macOS/BSD workarounds, no Windows paths, no POSIX-only restrictions. ## Script Foundation ```bash #!/usr/bin/env bash set -Eeuo pipefail shopt -s inherit_errexit readonly SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd -P)" trap 'printf "Error at %s:%d\n" "${BASH_SOURCE[0]}" "$LINENO" >&2' ERR trap 'rm -rf -- "${_tmpdir:-}"' EXIT ``` - `-E` propagates ERR traps into functions - `inherit_errexit` propagates errexit into `$()` command substitutions - Always create temp dirs under the EXIT trap: `_tmpdir=$(mktemp -d)` ## Core Rules - Quote every expansion: `"$var"`, `"$(cmd)"`, `"${array[@]}"` - `local` for function variables, `local -r` for function constants, `readonly` for script constants - `printf '%s\n'` over `echo` — predictable behavior, no flag interpretation - `[[ ]]` for conditionals; `(( ))` for arithmetic; `$()` over backticks - End options with `--`: `rm -rf -- "$path"`, `grep -- "$pattern" "$file"` - Require env vars: `: "${VAR:?must be set}"` - Never `eval` user input; build commands as arrays: `cmd=("grep" "--" "$pat" "$f"); "${cmd[@]}"` - Separate `local` from assignment to preserve exit codes: `local val; val=$(cmd)` ## Safe Iteration ```bash # NUL-delimited file processing while IFS= read -r -d '' f; do process "$f" done < <(find /path -type f -name '*.log' -print0) # Array from command output readarray -t lines < <(command) readarray -d '' files < <(find . -print0) # Gl...