On 15-11-25 04:52 PM, Alex Pilon wrote: >>> What's odd is that `find -xdev -- foo` doesn't work, yet `find -- >>> foo` does. I expected -- to be properly interpreted as the end of >>> options indicator, as per the manual. >> >> In the case 'find -xdev --' the '--' is coming after the first >> expression because '-xdev' is a predicate. >> >> In the case 'find -- foo' the '--' is coming before the first >> expression because 'foo' is a path. >> >> This is entirely consistent with the manual. The optional '--' just >> has to come before the first expression if something that could be >> ambiguously interpreted as an option is an argument to an expression. > > That's what I'm doing… > > $ touch ./-f > $ find -- -f > find: unknown predicate `-f' > > So let's double-check the man page. > > find(1): > A double dash -- can also be used to signal that any remaining > arguments are not options > > So the remainder are treated as expressions, "real options", or paths? > I'd have thought that the remainder would be treated as paths. Are you > saying that they're treated as expressions (like -name, -whatever as > long as it isn't -H and friends)?
Yes, that's exactly it. Anything after the '--' is treated as a path or an expression. Paths must come before expressions. Expressions start with a predicate. > find(1): > (though ensuring that all start points > begin with either `./' or `/' is generally safer if you use > wildcards in the list of start points). > > This parenthesis would make me think that the remaining get treated as > paths, not expressions. I can do what this says, nearly trivially, but > that just seems wrong. The parenthetical is talking about globbing behaviour of the shell. > I just wanted to protect any paths passed through to find in the code > below. > > diff --git a/pax b/pax > index 9b7de7d..dae4555 100755 > --- a/pax > +++ b/pax > @@ -78,7 +88,9 @@ if args.mode == 'write': > if args.x is None: > bsdcpio_args += ['-H', 'pax'] > if len(args.args) > 0: > - find = subprocess.Popen(['find', '--'] + args.args, > stdout=subprocess.PIPE) > + find_args = ['-xdev'] if args.X else [] > + find = subprocess.Popen(['find'] + find_args + ['--'] + > args.args, > + stdout=subprocess.PIPE) > bsdcpio_stdin = find.stdout > else: > bsdcpio_stdin = None > > I suppose that I could just use a list comprehension but that wouldn't > be the perfect and simplest way. > > I just wanted -xdev to be unambiguously an expression, -- treated as the > options delimiter, and everything after a path. The usage of the Unix 'find' command is this. find [options] [paths] [expressions] All paths must come before all expressions. What it doesn't say is options can be intermixed with paths and expressions, which can lead to ambiguity. -- Stephen M. Webb <stephen.w...@bregmasoft.ca> _______________________________________________ Linux mailing list Linux@lists.oclug.on.ca http://oclug.on.ca/mailman/listinfo/linux
