Bash operator

Answer quick Bash questions with a compact reference for strict mode, quoting, parameter expansion and defaults, test operators, conditionals and loops, arrays, functions, redirection, process substitution, exit status, and the common text and file commands. Use when someone asks for Bash syntax, how an expansion or test operator is written, or wants a fast lookup rather than a guided workflow.

Inspect which shell is running and which one a script will use, the Bash version and available features, enabled shell options, PATH and command resolution, exported variables, startup file order, and locale settings, without changing anything. Use before writing or running a script, when a command behaves differently in a script than in a terminal, when a Bash feature is unavailable, or when the user asks whether the shell is set up.

Find, inspect, copy, move, archive, and delete files from the shell with previewed and scoped commands, covering find predicates, safe deletion, permissions and ownership, symlinks, disk usage, atomic writes, and handling filenames with spaces or leading dashes. Use when files must be located or reorganized, when disk space must be traced, when permissions are wrong, or before running any command that removes or overwrites files.

Wire Bash scripts into the systems that run them, covering package scripts, continuous integration steps, Git hooks, cron and systemd timers, container entrypoints, argument and environment contracts, exit codes as gates, logging to a collector, and locking so two runs cannot overlap. Use when a script must run on a schedule, in a pipeline, on commit, or as a container entrypoint, or when a script works by hand but not where it is actually invoked.

Run, background, monitor, and stop processes from the shell, covering exit status and PIPESTATUS, job control, nohup and disown, signals and graceful termination, waiting on background work, timeouts, port and file holders, resource usage, and identifying a process precisely before killing it. Use when a command must run in the background or under a timeout, when a port is occupied, when a process must be stopped, or when a script hangs.

Write and repair Bash scripts with strict mode, correct quoting, argument parsing and validation, functions and local scope, arrays, cleanup traps, temporary files, clear exit codes, and messages on the right stream. Use when a script must be written or restructured, when a script fails silently or continues past an error, when word splitting breaks on filenames with spaces, or when temporary files are left behind.

Install a current Bash alongside the system shell, choose the right startup file for a setting, extend PATH without breaking it, add shellcheck and shfmt, and set up an executable script skeleton with a shebang that resolves to the intended interpreter. Use when Bash is too old for a needed feature, when a PATH or environment change must persist, when script tooling is missing, or when a new script must be scaffolded.

Lint and test Bash scripts, covering shellcheck severity and directives, shfmt formatting, syntax-only parsing, bats test structure with setup and teardown, stubbing external commands, asserting exit status and output, testing failure paths, and running the checks in a pipeline. Use when a script needs coverage or linting, when shellcheck reports warnings that must be understood or suppressed, or when a script's failure behaviour has never been exercised.

Filter, extract, and transform text at the shell with grep, sed, awk, cut, sort, uniq, tr, jq, and xargs, covering pattern choice, field handling, in-place editing, delimiter and locale pitfalls, streaming large files, and building pipelines that fail loudly. Use when text or log output must be searched, reshaped, counted, or converted, or when an existing pipeline returns the wrong fields or silently produces nothing.

Diagnose failing or misbehaving Bash scripts from reproducible evidence, covering syntax and interpreter mismatches, unbound variables, word splitting, silent pipeline failures, missing commands and PATH differences, permission and line-ending problems, hangs waiting on input, traps not firing, and exit codes. Use when a script fails, produces wrong output, works in a terminal but not in a script or cron job, or hangs without finishing.