Test for file(s): glob or -e?

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

This seemingly simple problem is stumping me. I want a concise way to test an arbitrary file "pattern" to see if the file(s) exist. The string to be tested can be in the format of a single filename, or a shell pattern such as "*.txt", "job[0-9].txt", "log.00?", etc.

I can use a -e test for a single filename, and a glob test for a pattern. What I'm looking for is a single test to use if I don't know ahead of time if the string will refer to a single file or a shell pattern.

Running a few tests with perl one-liners gives me this:

$ ls *.txt
javastuff.txt  modules.txt
$ perl -le '$,=" "; print glob "*.txt"'
javastuff.txt modules.txt
$ perl -le '$,=" "; print glob "joe.txt"'
joe.txt
$ perl -le '$,=" "; print glob "joe.txt*"'

$ perl -le 'print ((-e "joe.txt")?"yes":"no")'
no
$ perl -le 'print ((-e "*.txt")?"yes":"no")'
no
$ perl -le 'print ((-e "modules.txt")?"yes":"no")'
yes
$
[download]

Note the false positive for joe.txt in the glob test, and the problem with *.txt in the -e test.

I am currently using a hack that appends an asterisk (*) to the string I'm testing, and testing it with a glob command, e.g.,
if ( @files = glob $pattern.'*' ) {...
but there is an edge case where I only want "file" when "file1" and "file2" also exist, and that needs to be accounted for.

Any suggestions? Thanks.

Comment on Test for file(s): glob or -e? Select or Download Code

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•Re: Test for file(s): glob or -e? by merlyn (Sage) on Feb 18, 2004 at 13:15 UTC
What I'm looking for is a single test to use if I don't know ahead of time if the string will refer to a single file or a shell pattern. You can't know. A file named `abc[d]e` is perfectly legal, and yet using that string as a glob won't match that filename! You have to change your spec so that it is clear whether the string is a literal or a pattern. Anything else is going to get you into trouble. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l]
Re: •Re: Test for file(s): glob or -e? by delirium (Chaplain) on Feb 18, 2004 at 18:37 UTC
Changing the spec it is, then. I can enforce a 'files must have no shell wildcard characters in their names' policy with this. With that in mind, and after thinking over the problem some more, I came up with a test (update: the same test the ysth beat me to by 3 minutes) that seems to work: `if ( grep {-e} glob $file ) {...` [download] In this way, if $file is a single filename that doesn't exist, it will fail on the -e test. If $file is multiple files, glob will see them all.	[reply] [d/l]
Re: Test for file(s): glob or -e? by inman (Curate) on Feb 18, 2004 at 14:50 UTC
Try testing your data for 'globbable' characters. (My list of '' and ? is probably incomplete.) `#! /usr/bin/perl -w $, = ', '; print $ARGV[0] =~ tr/?// ? glob ($ARGV[0]) : ((-e $ARGV[0]) ? $ARGV[0 +] : '<No File>');` [download] This was tested on Win32 so $ARGV[0] is not globbed by the OS. Also try the following which atempts a glob followed by a single file test in case you were globbing a normal file name. `#! /usr/bin/perl -w $, = ', '; my @files = glob('*.txt'); print @files if -e $files[0];` [download]	[reply] [d/l] [select]
•Re: Re: Test for file(s): glob or -e? by merlyn (Sage) on Feb 18, 2004 at 15:27 UTC
But * and ? are valid filename characters, so how can you know if I was giving you a literal filename, or a glob? -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re: •Re: Re: Test for file(s): glob or -e? by inman (Curate) on Feb 18, 2004 at 18:46 UTC
My Windows background has found me out... `$, = ', '; my @files; print ((-e $data)? $data : ((@files = glob $data) && ($data ne $files[ +0]))? @files : ()) if $data;` [download] Prints $data if $data is a file. Prints the globbed $data only if the glob did some work. The whole statement is protected just in case $data is empty.	[reply] [d/l]
Re: Test for file(s): glob or -e? by ysth (Canon) on Feb 18, 2004 at 18:34 UTC
I have to agree with merlyn (not that it's a struggle :) that you should specify that your input is either a filename or a glob pattern, but maybe this will help: `# get the names if any @files = grep -e, glob $pattern;` [download] or `# do any exist? if (grep -e, glob $pattern) {...` [download]	[reply] [d/l] [select]
Re: Re: Test for file(s): glob or -e? by Anonymous Monk on Feb 18, 2004 at 18:44 UTC
boggles Why grep -e? Does glob make up stuff that doesn't exist in the directory now?	[reply]
Re: Re: Re: Test for file(s): glob or -e? by ysth (Canon) on Feb 18, 2004 at 18:57 UTC
By design, glob only checks for actual existence of files if you include * or ? in that part of the path: `$ echo hi there>foo $ ls foo $ perl -wle'print for glob "{a,b,c,}fo{,}"' afo bfo cfo foo fo` [download] This pattern expands to {afo,bfo,cfo,fo,afo,bfo,cfo,fo}. Only the subpatterns containing a ? or will be restricted to what exists. In the simple case, glob "joe.txt" will always return joe.txt.	[reply] [d/l]