How to match name exactly with Bash's `help` builtin?

Question

It seems the Bash built-in help command help does some really strange globbing:

help read shows the documentation for read, readarray and readonly.
help rea? shows only the documentation for read.
help 'read$' doesn't work.
help read | sed '/^read[^:]\+/,$d' is just silly.

Is there some more intuitive way to get only the read output?

It seems they have fixed this annoying behaviour with the implicit `*` at the end if there is an exact match, (at least as of version version 4.3.42). In my version of bash `help read` shows only the documentation for `read`, but `help read` would show the documentation for `read`, `readarray`, etc. — Elmar Zander, Nov 27 '15 at 08:25

score 3 · Accepted Answer · answered Feb 25 '13 at 18:50

3

It seems by defaul help foo is actually equivalent to help foo*. But if some special globbing characters are used then the ending "*" is not implicitely added.

So, a possibility would be help [r]ead.

The globbing used is the one used by the shell for file matching; afaik there isn't any equivalent of \< nor \>.

answered Feb 25 '13 at 18:50

Pablo Saratxaga

2,491
26
16

It's globbing, just like filename completion, *but it is expanded after you enter it*, and I don't see anyway to control it (see `builtins/help.def`, it's a `for()` loop over all builtins). Since `[]` trumps `*`, `[r]ead` gets my vote. `read`, `time` and `type` are the only problematic complete commands (and the two types of `for` if you're a pedant). – mr.spuratic Feb 25 '13 at 21:43
Accepting since it also works for `help [s]et`. – l0b0 Feb 26 '13 at 07:54

score 0 · Answer 2 · answered Feb 25 '13 at 21:08

pipe the output of help through a small awk script:

help () {
    builtin help "$1" |
    awk -F: -v command="$1" '
        p && /^[^[:space:]]/ {exit}
        $1 == command {p = 1}
        p
    '
}

Now help read will only give you the help for the read builtin.

How to match name exactly with Bash's `help` builtin?

2 Answers2

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