On 21/10/15 13:56, Eric Blake wrote:
> On the libvirt list, the question was raised on what happens if you have
> a long command line, but then forget the arguments of an option that
> requires an argument, so you try to add --help in-place to learn them.
> For example:
>
> $ ls --block-size --help
> ls: invalid --block-size argument '--help'
>
> Okay, this makes sense, '--help' is appearing in the argument position,
> not as an option, so it got eaten by --block-size, and we don't get
> help. So let's try again, by placing a filler for the option argument,
> then our real --help attempt; and since --help is idempotent, it doesn't
> matter how often it appears up front, so let's use --help as the filler:
At this stage it might be a simpler thought process
for users to just `ls --help` rather than expecting
adding another --help to work. Also the typing it saves
is the command name vs {Up}, i.e. not much.
I'd be 60:40 against complicating the commands for that.
As for alternatives, you could:
!!:0 --help
Or setup and alias to do that:
alias lh='`history -p \!\!:0 --help`'
New users could use the standard: command --help,
while power users saving time could do the above.
This also works with bash >= 4.4 which now supports --help.
Also relate would be integrating `explain¹` functionality
into the man page system or whatever,
with associated shortcut alias or in .inputrc to access that.
alias ex='`explain history -p \!\!`'
That would have the advantage of narrowing the explanation
to the options used.
thanks,
Pádraig.
¹ https://www.mankier.com/blog/explaining-shell-commands-in-the-shell.html
