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When writing scripts for other shells, it can be confusing and annoying that our `man` function shadows other manual pages, for example `exec(1p)` from [Linux man-pages]. I almost never want to see the fish variant for such contended cases (which obviuosly don't include fish-specific commands like `string`, only widely-known shell builtins). For the contented cases like `exec`, the POSIX documentation is more substantial and useful, since it describes a (sub)set of languages widely used for scripting. Because of this I think we should stop overriding the system's man pages. Nowadays we offer `exec -h` as intuitive way to show the documentation for the fish-specific command (note that `help` is not a good replacement because it uses a web browser). Looking through the contended commands, it seems like for most of them, the fish version is not substantially different from the system version. A notable exception is `read` but I don't think it's a very important one. So I think we should can sacrifice a bit of the native fish-scripting experience in exchange for playing nicer with other shells. I think the latter is more important because scripting is not our focus, the way I see it. So maybe put our manpath at the end. In lieu of that, let's at least have `exec.rst` reference the system variant. [Linux man-pages]: https://www.kernel.org/doc/man-pages/ Closes #10376
60 lines
2.0 KiB
ReStructuredText
60 lines
2.0 KiB
ReStructuredText
.. _cmd-trap:
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trap - perform an action when the shell receives a signal
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=========================================================
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Synopsis
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--------
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.. synopsis::
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trap [OPTIONS] [[ARG] REASON ... ]
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Description
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-----------
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.. only:: builder_man
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NOTE: This page documents the fish builtin ``trap``.
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To see the documentation on any non-fish versions, use ``command man trap``.
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``trap`` is a wrapper around the fish event delivery framework. It exists for backwards compatibility with POSIX shells. For other uses, it is recommended to define an :ref:`event handler <event>`.
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The following parameters are available:
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*ARG*
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Command to be executed on signal delivery.
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*REASON*
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Name of the event to trap. For example, a signal like ``INT`` or ``SIGINT``, or the special symbol ``EXIT``.
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**-l** or **--list-signals**
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Prints a list of signal names.
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**-p** or **--print**
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Prints all defined signal handlers.
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**-h** or **--help**
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Displays help about using this command.
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If *ARG* and *REASON* are both specified, *ARG* is the command to be executed when the event specified by *REASON* occurs (e.g., the signal is delivered).
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If *ARG* is absent (and there is a single *REASON*) or ``-``, each specified signal is reset to its original disposition (the value it had upon entrance to the shell). If *ARG* is the null string the signal specified by each *REASON* is ignored by the shell and by the commands it invokes.
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If *ARG* is not present and **-p** has been supplied, then the trap commands associated with each *REASON* are displayed. If no arguments are supplied or if only **-p** is given, ``trap`` prints the list of commands associated with each signal.
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Signal names are case insensitive and the ``SIG`` prefix is optional. Trapping a signal will prevent fish from exiting in response to that signal.
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The exit status is 1 if any *REASON* is invalid; otherwise trap returns 0.
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Example
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-------
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::
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trap "status --print-stack-trace" SIGUSR1
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# Prints a stack trace each time the SIGUSR1 signal is sent to the shell.
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