Question

71

How to make `man` work for shell builtin commands and keywords?

rated 0 times [ 71] [ 0] / answers: 1 / hits: 5991 / 3 Years ago, mon, october 11, 2021, 4:07:19

I use the man command all the time when I want to get information about a specific command. But this doesn't help me too much when that specific command is a shell builtin. For example:

man cd

returns:

No manual entry for cd

My question is: it is possible to make man also work for all shell builtin commands (like cd, alias, history, etc.), and keywords (like if, while, [[, {, etc.)?

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dileble

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answered 3 Years ago nguai · Accepted Answer

The help command when is used with -m option can display information about builtin commands in pseudo-manpage format. For example:

help -m cd | less

will display information about cd command in a format almost exactly like in a manual page.

Starting from this command you can wrap man command in one function in your .bashrc file as follow:

man () {

    case "$(type -t -- "$1")" in

    builtin|keyword)

        help -m "$1" | sensible-pager

        ;;

    *)

        command man "$@"

        ;;

    esac

}

After this man will work also for all shell builtin commands and keywords. For example:

man :

will display:

NAME

    : - Null command.



SYNOPSIS

    :



DESCRIPTION

    Null command.



    No effect; the command does nothing.



    Exit Status:

    Always succeeds.



SEE ALSO

    bash(1)



IMPLEMENTATION

    GNU bash, version 4.2.45(1)-release (x86_64-pc-linux-gnu)

    Copyright (C) 2011 Free Software Foundation, Inc.

    License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>