Wheeler: Fixing Unix/Linux/POSIX Filenames [LWN.net]

Wheeler: Fixing Unix/Linux/POSIX Filenames

Posted Mar 26, 2009 21:11 UTC (Thu) by explodingferret (guest, #57530)
In reply to: Wheeler: Fixing Unix/Linux/POSIX Filenames by epa
Parent article: Wheeler: Fixing Unix/Linux/POSIX Filenames

Well, this is a good point. There are basically two uses of shell scripts:

1) Portable scripts (of a kind), init scripts, and build scripts. In all these cases the scripts need to have #!/bin/sh at the top, and contain just about every fix for every problem ever, including [ "x$var" = x ] and ${1:-"${@}"} and various other monstrosities.

In these scripts, the quotes around variables; ./ in front of filenames; IFS= for read; and filename=`foo; printf x`; filename="${filename%x}" crap will *always* have to be there. So no point trying to fix anything for those.

2) The other use is scripts that are used on either one system (personal scripts) or one "class" of system, like "only Debian GNU/Linux".

These scripts can use a particular shell like #!/bin/bash and assume the existence of -print0 and -printf to find and -d '' to read and all the other little conveniences which make a lot of the problem go away.

Well, other than newlines at the end of filenames. That's the only case that I refuse to take account of in my scripts, unless security issues might arise.

----

I'm not saying that I disagree with the ideas in this article (although I'd like to keep spaces and shell special characters in my filenames, actually). I'm just saying that as far as shell scripting is concerned, it may not actually help all that much. The main gain for me would be the security fixes and less typing in my interactive shell. Even though I'm pretty sure I don't have any newlines or control characters in any of my filenames, I just can't bring myself to write bad scripts, and that's kinda sad.

to post comments

Wheeler: Fixing Unix/Linux/POSIX Filenames

Posted Mar 28, 2009 1:18 UTC (Sat) by nix (subscriber, #2304) [Link] (2 responses)

At work I co-maintain scripts in a third class: scripts that come with
an 'appliance' (for this purpose, a set of software which is the raison
d'etre of the hardware for which it is bought: this could be a tiny
embedded system or a giant bank database or simulation box). In this case,
they can dictate whatever shell they damn well like.

I dictated zsh 4, simply because for this application C was far too
unpleasant, ksh was too buggy (thanks, Linux, for pdksh, with its broken
propagation of variables out of loops-with-redirection), and there was no
hope of getting the clients' systems people to install Perl: but they were
perfectly happy to install a recent zsh: fewer dependencies and no scary
modules (well, actually zsh *does* have a module system but they didn't
realise that!)

Wheeler: Fixing Unix/Linux/POSIX Filenames

Posted Nov 15, 2009 1:06 UTC (Sun) by yuhong (guest, #57183) [Link] (1 responses)

"ksh was too buggy (thanks, Linux, for pdksh, with its broken
propagation of variables out of loops-with-redirection)"
Was ksh93 tried?

Wheeler: Fixing Unix/Linux/POSIX Filenames

Posted Nov 15, 2009 13:15 UTC (Sun) by nix (subscriber, #2304) [Link]

zsh93 was too sodding hard to require because building it was a nightmare.
At the time it wasn't free enough either.