Grep man pages by sections

about.zsh

#!/usr/bin/env zsh
# -*- encoding: utf-8 -*-
# Copyright (c) 2015 by Peter Hillerström
# License: MIT License

# This can be sourced from zsh dotfiles. If you don't care about other
# functions than `about`, put them inside the about function.
# Output can be piped to GNU `fmt -s` command for nice formatting.

about() {
    # Grep manpages by sections
    local cmd=$1; shift
    man $cmd | grep_sections $* | doublelines
}

striplines () { ruby -ne 'puts $_.strip' }
removehyphens () { perl -pe 's/-$//' }
doublelines () { perl -pe 's/\n/\n\n/' }

null_separate_sections () {
    # Read whole input at once with -0777
    ruby -0777 -pe 'gsub(/\n\n/, "\0")' | perl -pe 's/\n/ /'
}

grep_sections() {
    # Grep input by sections (separated by two newlines)
    grep -B8 -A24 $* | striplines | removehyphens | null_separate_sections | \
        xargs -0 -n1 echo | \
        grep $*
}