Re: `set completion-ignore-case on' does not work well for the first word on command line

[Chet Ramey]

Jian Wang wrote:
> On Feb 17, 2008 5:21 AM, Chet Ramey <chet.ramey@case.edu 
> <mailto:chet.ramey@case.edu>> wrote:
>
>     Jian Wang wrote:
>      > When using Bash, I often turn on the `completion-ignore-case'
>     option of
>      > readline. It works fine for most cases but sometimes it does not
>     work as
>      > expected when completing the first word on the command line. For
>     example,
>      > there is a bash script ~/MyDir/Foo.sh, on command line, when I
>     input ~/my
>      > and then press TAB, the word is completed as ~/myDir . Is that a bug?
>
>     It's not really a bug, since case-ignoring does not necessarily mean
>     case-changing (this is usually called `case-preserving').  Readline uses
>     what's found in the file system rather than preserving what the user
>     typed, though, as you noticed when you tried to do word completion
>     instead
>     of command completion.  It might be useful to emulate Readline's
>     behavior
>     while doing command word completion.
>
> Thanks for your reply but I'm a bit confused. You said that readline 
> uses what's found in the file system rather than preserving what the 
> user typed. But for my example, ~/MyDir should be found in the file 
> system but why it's completed as ~/myDir? Readline behaves differently 
> between word completion and command completion?  Or, command completion
> is done by Bash itself other than readline?

Readline does a fine job of completing filenames in the current
directory, or completing a full pathname.  Since command completion
is inherently application-specific and doesn't match well with that
limited set of capabilities, bash does it internally, only resorting
to readline in a couple of cases.  The way bash does things results
in this one specific instance differing from readline's filename
completion.

> And I noticed that if I 
> first input /home/myname/my and than press TAB, it'll be correctly 
> completed as /home/myname/MyDir . What's the difference?

The tilde prefix, which needs to be expanded so pathnames can be checked
for the correct attributes (e.g., executability) and then removed.  If
you look at the code, you'll see that bash appends the remainder of a
completed pathname to what the user typed, which includes the tilde
prefix, since the rest of the code has to expand the tilde prefix before
doing the checking it needs to.

Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                       Live Strong.  No day but today.
Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/