Linux – How to Make the ‘Man’ Utility as Comprehensive as ss64.com

Having a man page for read (in section 1 of the manual) that says anything else than "There is no read command, but your shell might have a read builtin command, see your shell manual for details" is misleading, because read is a shell builtin and the behaviour and supported options vary from shell to shell.

Some systems (generally not Linux ones) however do have a read command (in /bin, /usr/bin or elsewhere) as POSIX requires (but the Linux Standard Base (LSB) specification lifts that requirement), and on those systems, the man page will describe the behaviour of that read command, and will be misleading because it's generally not that read that you invoke when you call read at a shell prompt or in a shell script or in system(), popen()... but the shell builtin one.

That http://ss64.com site describes the bash builtin read command (though it doesn't say which version of bash, and for instance, it's different from the read builtin in the version of bash on this machine, which itself is different from that read from the bash of another (older) machine I have access to) in a bash section. In that regard, it's not misleading, but where it's very misleading is where it puts all sorts of other non-bash related commands in that same section and sort of implies that bash (one of many shells available on Linux and other Unices, shells being one of many ways to run commands) is necessary to run those commands or that those commands have anything to do with it.

Now, when you do man read, if there's no read command in section 1 (user commands) of the manual, it will search in other sections. For instance, if you have installed the manpages-dev package (on Debian), you'll get the man page of the read system call (in section 2). If not, but you have installed the TCL documentation package, you'll get the man page for the read TCL function in section 3tcl.

You can ask explicitly for the read user command with man 1 read (man -s 1 read on some systems). If your manual had a 1bash section, it would bring it up before the one in section 1zsh, so you'd need to write it man 1zsh read to get the zsh variant. You can get all the man pages with man -a read, you can find out what packages they come from on Debian with: dpkg -S $(man -wa read). For instance, on this system, I have:

$ dpkg -S $(man -wa read)
9base: /usr/share/man/man1/plan9-read.1.gz
tcl8.5-doc: /usr/share/man/man3/read.3tcl.gz
manpages-dev: /usr/share/man/man2/read.2.gz

With zsh, pressing Alt-H at the prompt brings the manual (via the man command) for the command you're currently typing. The default zsh installation on Debian improves it to make use of the run-help function (see info -f zsh --index-search=run-help), so you get help for the builtins as well.

With the fish shell, there's a help builtin function that tries to bring the most sensible documentation for a given command or fish concept (from man or the fish documentation).

If for some reason, you're forced to using bash (grin) or can't be bothered to change from the default, bash also has a help builtin command that brings help on bash builtins (however note that help read is like help '*read*', that is it brings the manual for all the builtins whose name contains read, use help '[r]ead' for instance, if you only want the read manual).

bash's help only works for bash builtins. If you want to extend it to include search in the manual in sections 1 (user commands) and 6 (games) and 8 (administrative commands), you could redefine it as:

help() {
  builtin help "$@" 2> /dev/null ||
    MANSECT=1:8:6 man "$@"
}