Changed handling of "!" in /bin/sh?

Eric Blake ebb9@byu.net
Tue Jan 16 02:58:00 GMT 2007


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According to Luke Kendall on 1/15/2007 7:39 PM:
> I have a script that starts #!/bin/sh which has occasional things like
> the use of an exclamation mark in a string, or a case statement to
> accept an exclamation mark to throw a shell, which has stopped working
> now that I've upgraded to a non-ancient Cygwin (i.e. now that sh ==
> bash).

Simple test case, please?

> 
> It seems that /bin/sh is now trying to interpret "!" as bash would! 
> How can I make /bin/sh work like a Bourne shell, globally?

You can't.  Bourne shell is obsolete (unless you are on Solaris, and are a
die-hard to use their /bin/sh instead of /usr/xpg4/bin/sh), because it
lacks functions, ${} command substitution, and other useful features of
modern shells.  Rather, you can make /bin/sh behave like a POSIX shell -
you do that by invoking bash as /bin/sh instead of /bin/bash (ie. you are
ALREADY getting POSIX behavior).  ash was slowly moving in this direction,
but had its own set of bugs.  If your legacy scripts don't behave properly
with /bin/sh, then most likely, it is a bug in your script according to
the rules of POSIX, that just happened to work with ash because of a
matching bug in ash.

> 
> The same script works fine if run by ash instead of bash, and it also
> works fine under Linux (where sh is bash), so it seems like there's
> some problem with bash's emulation of sh under Cygwin.

That's a pretty harsh claim without a sample script to back it up.  I try
very hard to make Cygwin's /bin/sh exactly like Linux's /bin/sh.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             ebb9@byu.net
volunteer cygwin bash maintainer
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