Can I get individual man pages for the bash builtin commands?

Question

Is there anywhere you can download a manpage for every builtin commands?

I know you can just use help or man bash and search to find info about it, but I want them separated, so I can just do man read and get the read manpage.

Solution 1

Try this:

bashman () { man bash | less -p "^       $1 "; }

You may have to hit n a couple of times to get to the actual command instead of a paragraph that happens to have the command name as the first word.

Explanation: this pipes the entire output of man bash, i.e. bash's entire man page (which is a huge document, and has subsections explaining each bash builtin command) to the reading program less. less' -p flag stands for "pattern"; what it does is automatically scroll to the first point in the input text that matches the pattern. The pattern here is a regex which matches "The start of a line (^), followed by a specific number of spaces, followed by ..." – and here, bash inserts the first argument provided to the bashman function, because bash sees the special $1 token (which means "the first argument") in a string delimited with double-quotes (single quotes would tell bash that you literally mean the characters $1). So, if you run bashman cd, you will effectively be searching for any line in bash's man page with starts with a bunch of spaces, then the string "cd". Because there might be other points in bash's entire man page that also match this pattern besides the actual heading of the section that explains, eg., "cd", this function may not actually take you to the correct part of the bash man page.

Solution 2

help read
help read | less

In zsh:

run-help read

or type read something and press M-h (i.e. Alt+h or ESC h).

If you want to have a single man command so as not to need to know whether the command is a built-in, define this function in your ~/.bashrc:

man () {
  case "$(type -t "$1"):$1" in
    builtin:*) help "$1" | "${PAGER:-less}";;     # built-in
    *[[?*]*) help "$1" | "${PAGER:-less}";;       # pattern
    *) command -p man "$@";;  # something else, presumed to be an external command
                              # or options for the man command or a section number
  esac
}

Comments

[mattdm]

It's not quite what you want, but on my Fedora 15 system, these are separated into separate man pages which reference a builtins (1) man page. This is still a big aggregate document, but at least it's just the builtins and not everything to do with bash.

[Tyilo]

Doesn't work in Mac OS X

[suspectus]

Nor does man builtins work on linux mint.

[Loves Probability]

If all that you need is to know about a built in, Just use help <BuiltinName> -- Hope it helps those people like me annoyed on the failure of man and info with famous builtins. E.g. help command to know about the great yet less used command command. Finally as the question also hints, the help alone simply lists all possible builtins. (Verified on Ubuntu 16.04).

[Gilles 'SO- stop being evil']

Good idea. Not what I think Tyilo wants, but I'm not convinced I got that right.

[Tyilo]

Works perfect! Adding a space after $1 makes it better

[Chris Perkins]

type -t gives and empty string for a pattern. How does this work? *[[?*]* ?

[Gilles 'SO- stop being evil']

@balki type looks up an exact name. I don't think there's a way to look up a pattern, short of having a hard-coded list of built-ins and doing some complicated parsing of the output of alias, typeset -f and $PATH lookups.

[thomanil]

You can also use LESS=-p"^ $1 " man bash. That way, you're not stripping any escape sequences.

[Gilles 'SO- stop being evil']

@spex No, I meant “i.e.”. It's followed by a complete list, not by some examples.

[spex]

@Gilles your list is not exhaustive and not universal, they are examples, thus e.g.

[Admin]

run-help does display help for built-in, if it's not built-in it will open the man-page for that tool. Good tip.

[Luke Davis]

You can also create a function that wraps around the original man function: function man() { local binman=/usr/bin/man; if ! $binman $1 &>/dev/null; then echo "No man entry for \"$1\"."; elif $binman bind | grep "BSD General Commands Manual" &>/dev/null; then LESS=-p"^ $1 " $binman bash; else $binman $1; fi; }.

[rugk]

Actually, help set and run-help set, all present exactly the same as man here! So this is no solution. Note I am using zsh.

[rugk]

As I've explained here too this often does not work. As you stated, you often get to "a paragraph that happens to have the command name as the first word". As such, this question is not completely answered…

[Jonathan Komar]

Ironically, man help fails, haha! It requires a recursive-looking call help help.

[ijoseph]

Similar for zsh: zshman () { man zshbuiltins | less -p "^ $1 "; }

[Admin]

instead, I do this: $man bash builtins - opens a dedicated man page. Then search e.g. for shopt [. Advantage of this approach is that is a method so it's immediately transferable. Disadvantage is that you have to remember it;)