Changes for version 0.18 - 2026-09-24
- Fixed
- **A command that could not be launched was reported as a success, and the rest of the calling program ran twice.** `system()` forks and then execs; when the exec fails, its child warns "Can't exec", which the module's `use warnings FATAL => 'all'` turned into a die *in that forked child*. The die unwound out of `task()` into the caller's program, which then ran on as a second copy, while the parent was handed the copy's exit status. `task(cmd => 'no-such-program', die => 0)` came back `exit => 0`, `will.do => 'done'`, and every later step ran twice. The `timeout` path had the same defect in its own fork. A command that cannot be launched is now `exit => -1` (`127` under a `timeout`) and `FAILED`. A string with a shell metacharacter in it was never affected, since the shell launches the program and reports `127` itself.
- **A one-element array-ref `cmd` went through the shell.** An array ref is documented as run without a shell, but `system(@list)` hands a list of one to the shell, so `cmd => ['echo hi; rm x']` ran both commands. The array form now always runs the named program directly.
- **A command finishing at the moment its `timeout` fired could be reported as timed out, with `exit => -1`.** If the alarm arrived after the child had been reaped but before it was cancelled, the group was killed anyway and a second `waitpid` overwrote the real status. The group is now killed only if the child has not already been reaped. The window is a few instructions wide, and has no test.
- Performance
- **`stdout` and `stderr` are captured without `Capture::Tiny`.** It slurped each capture into a lexical and returned it through several list copies, which perls before 5.20 do not share: a `task()` whose command printed 100 MB peaked at 498 MB RSS and took 0.53 s on perl 5.10.1. `task()` now points descriptors 1 and 2 at temporary files itself, with `POSIX::dup2`, and reads each file straight into the record: 108 MB and 0.17 s. The capture is read back through the caller's own `STDOUT` and `STDERR` layers, as `Capture::Tiny` did, so a caller that set `:encoding(UTF-8)` still gets characters; standard descriptors the caller had closed are plugged with the null device for the run and closed again after.
- **Trailing whitespace is stripped by walking back from the end.** The regex used before scanned the whole of `stdout` from the start, and on a perl with copy-on-write copied it first: on a 100 MB capture, 0.13 s and peak RSS from 107 MB to 205 MB on perl 5.44.0. End to end, a `task()` producing 100 MB of `stdout` went from 306 MB peak RSS and 0.30 s to 111 MB and 0.12 s on 5.44.0.
- **Printing the record no longer copies the captured output.** The clipped copy made for printing copied every field in full before clipping it, which perls before 5.20 do not share: on perl 5.10.1 that raised peak RSS from 205 MB to 303 MB for a 100 MB `stdout`.
- Changed
- **A caller whose `STDOUT` is an in-memory handle now has the command's output captured.** `Capture::Tiny` redirected the `STDOUT` glob, and a glob opened on a scalar has no descriptor, so the command wrote past it onto the real descriptor 1 — the terminal — and the record's `stdout` came back empty. The redirect is now on the descriptor, which is what the command inherits. A caller that relied on that output reaching the terminal will now find it in `stdout` instead.
- Packaging
- **`Capture::Tiny` is no longer a prerequisite at all.** The module captures on its own descriptors, and the tests use `t/lib/CaptureStd.pm`, a 46-line `capture {}` with the same calling convention that reopens the `STDOUT` and `STDERR` globs — deliberately not the module's own mechanism, so a bug in one cannot hide the same bug in the other. `File::Temp`, which is core, is now a runtime prerequisite.
- Tests
- **`t/03.fixes.t`**, one block per defect above except the race, and one for the in-memory `STDOUT`, each confirmed to fail against 0.17 first; and two covering the new capture's handling of closed descriptors and of output layers, which pass against 0.17 as well, since the point is that nothing changed there.
- Block 14 of `t/02.fixes.t` (`quiet => 1`) used to assert that the command's output escaped an in-memory `STDOUT`; it now asserts that the output is in the record.
Documentation
easy, simple workflow manager (and logger); for keeping track of and debugging large and complex shell command workflows
Modules
easy, simple workflow manager (and logger); for keeping track of and debugging large and complex shell command workflows