Shell & Bash Interview Questions and Answers

Both run a command for many files, but they differ in safety and performance.

find . -name '*.tmp' -exec rm -- {} +      # batches, handles spaces
find . -name '*.tmp' -print0 | xargs -0 rm --

-exec cmd {} \; runs the command once per file. -exec cmd {} + batches as many files as the argument limit allows, which is much faster and still handles spaces correctly.

xargs reads items from stdin and builds commands. By default it splits on whitespace and mishandles quotes and spaces, so pair find -print0 with xargs -0 for NUL-delimited input. Useful flags are -n1 to limit files per invocation, -P4 for parallelism and -I{} for substitution.

The main advantage of xargs is parallelism; -exec ... + avoids an extra process and is safer by default. Filenames can even contain newlines, so preview destructive commands with echo before running them.

A production script should be safe to re-run, fail clearly and clean up after itself.

#!/usr/bin/env bash
set -euo pipefail

workdir=$(mktemp -d)
cleanup() { rm -rf "$workdir"; }
trap cleanup EXIT ERR INT TERM

log() { printf '%s %s\n' "$(date -Is)" "$*" >&2; }

main() {
    if [[ $EUID -ne 0 ]]; then
        log "must run as root"
        exit 1
    fi
    mkdir -p /etc/myapp
    install -m 0644 config.toml /etc/myapp/config.toml
    systemctl is-active --quiet myapp || systemctl start myapp
    log "done"
}

main "$@"

Practices that matter: quote expansions, validate inputs and check tools with command -v, use mktemp for temporary files, and make actions idempotent by creating only what is missing and using install for exact permissions. Log to stderr, return meaningful exit codes, avoid unchecked cd, and document dry-run options.