strange behavior of csh_glob versus bsd

bcrowell2 has asked for the wisdom of the Perl Monks concerning the following question:

O monks,

I observe that the following two examples behave differently:

perl -e 'use File::Glob; while ($x=File::Glob::csh_glob "a.a") {print 
+"$x\n"; sleep 1} print "$x\n"'
perl -e 'use File::Glob; while ($x=File::Glob::bsd_glob "a.a") {print 
+"$x\n"; sleep 1} print "$x\n"'
[download]

The file a.a exists in the current working directory. The bsd_glob version does what I expect, which is to loop forever, but the csh_glob version exits after one iteration. Does anyone understand this? Thanks in advance,

-Ben

Comment on strange behavior of csh_glob versus bsd_glob Download Code

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Re: strange behavior of csh_glob versus bsd_glob by liverpole (Monsignor) on May 19, 2007 at 19:40 UTC
Hi bcrowell2, If you peek into the source for File::Glob, you'll see that `csh_glob` is a separate, undocumented method, which is not directly related to the method `GLOB_CSH` (which is documented, and just sets a bunch of flags). Furthermore, there's a comment: `# NOTE: The glob() export is only here for compatibility with 5.6.0. # csh_glob() should not be used directly, unless you know what you're +doing` [download] And finally, you'll see that there's a hash `%iter` (documented as "## borrowed heavily from gsar's File::DosGlob"), which is used the very first time to hold the results from `dos_glob`, and after that, returns the next value in the already-created list. s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/	[reply] [d/l] [select]
Re^2: strange behavior of csh_glob versus bsd_glob by bcrowell2 (Friar) on May 19, 2007 at 19:57 UTC
Hi all, Thanks very much for the replies. I originally just used the <> operator, which had the same behavior as csh_glob(). I could just as well have titled this "strange behavior of <> versus bsd_glob." It seems odd to me that <> would have this behavior, but anyway, now I know how to fix the problem: don't use <>, use bsd_glob. Thanks! -Ben	[reply]
Re: strange behavior of csh_glob versus bsd_glob by Zaxo (Archbishop) on May 19, 2007 at 19:36 UTC
`File::Glob::bsd_glob()` just calls the C library function `doglob()`, which is unlikely to be sensitive to the perl context. `File::Glob::csh_glob()` maintains an iterator over the list of results and does some wantarray checking to deliver either the whole list or one path at a time. That is an occasional perl convention. I expect bsd_glob() could be written that way, too. DWIM sometimes means doing what someone else means ;-) After Compline, Zaxo	[reply]