Run a shell command or text filter

Use installed local tools such as sort or tr from an editing buffer. The command prompt uses shell syntax. Source text is supplied only by the two region commands, as literal stdin data followed by EOF.

Show command output

Run M-x shell-command or modal :shell-command, enter printf 'hello\n' and press Return. Non-modal M-! opens the same prompt. Keep editing while it runs, then use shell-command-output to visit its read-only plain-text stdout. The command uses the source file's containing directory captured before the prompt. For an unnamed buffer it uses the explicitly opened directory, then the editor launch directory.

Transform a selection

Select a nonempty linear range. For the whole buffer in non-modal editing, use M-< C-SPC M->; modal Normal can use ggVG.

Run shell-filter-region (C-u M-| in non-modal editing), enter sort or tr a-z A-Z, then press Return. Complete successful stdout replaces only the captured range in one native edit. Undo once with C-x u or modal Normal u. Empty stdout deletes the region. The visiting file is not saved automatically.

Use shell-command-on-region (M-|) to inspect a transformation without editing. Use shell-command-insert (C-u M-!) to insert stdout at the captured point with no document input. Empty insertion leaves history unchanged.

Cancel or inspect a failure

C-g cancels an open shell prompt. To stop an active job, run shell-command-cancel or press C-g in its source after any inner prompt, search or popup has closed. A second job waits for explicit retry after cleanup; it is not queued. Normal quit consent remains in effect.

Use shell-command-output for the last retained stdout or failure diagnostics; C-x b can select *Shell Diagnostics* directly when status/stderr is separate. A changed or closed output identity is not recreated by that command.

A stale, closed, reloaded, rebound or newly read-only target rejects automatic publication. Inspect the retained output and run a fresh command against your current source. Nonzero status, invalid UTF-8/NUL, aggregate output overflow, timeout and cancellation do not publish a partial edit.

Configure the startup shell preferences when you need another installed shell or finite limits. See the User Guide exercise for a complete sort-and-undo workflow and the reference for all exact bounds and interaction rules.