Wiggins d'Anconia wrote:
Bret Goodfellow wrote:
Here's a simple perl script where I am listing out the contents of a
directory. When it completes, the following error occurs. How do I
eliminate this?
Use of uninitialized value in length at C:\BegPerl\deldir.pl line 23.
Below is the script:
#!/usr/bin/perl
# Dsrch1.plx
# use strict ;
If you comment out strictures they can't help you. Don't accept this
shortcut while learning, it teaches the wrong things. Turn it on.
use warnings ;
$directory = $ARGV[0];
my $directory = $ARGV[0];
opendir(DIR, $directory) or die "Can't open $directory\n" ;
Include $! in the error message so that you will know why it can't be
opened.
$direntry = readdir(DIR);
You are only reading the first entry in the directory handle. You need
to put this in list context, presumably with an array, to read them all.
my @list = readdir(DIR);
($mtime) = stat($direntry);
'mtime' is not the first element of the list returned by stat. You want
the 9th.
($mtime) = (stat $direntry)[9];
And presumably you want to do this in your loop.
#######################################################
# read entire directory contents and print out #
#######################################################
while (length($direntry) > 0) {
$direntry only contains the first value so this loop is pointless, see
the list comment above. And using length is probably not necessary,
since you can just use definedness to test for an entry since you won't
ever have an empty string directory.
foreach my $file (@list) {
print "$direntry - modify date: $mtime\n" ;
$direntry = readdir(DIR);
Now I see how you are doing your loop. The problem is that at the end of
the directory list, readdir returns undef, which is why you are getting
the warning about an uninitialized value. The loop runs, asks for the
next entry in the list, there aren't any more, then the loop does its
check again, on the empty value.
If you want to retrieve the entries one at a time (and large directory
lists could benefit from this) you can do the readdir in the while test,
while (my $file = readdir DIR) {
Which will bail when it hits the end of the list.
}
closedir(DIR);
use strict;
use warnings;
my $DIRHANDLE;
opendir $DIRHANDLE, "$ARGV[0]" or die "Can't open directory handle: $!";
while (my $file = readdir $DIRHANDLE) {
my $mtime = (stat $file)[9];
print "$file - modify date: $mtime\n";
}
closedir $DIRHANDLE;
Very good Wiggins, but you missed one very important point!
perldoc -f readdir
readdir DIRHANDLE
Returns the next directory entry for a directory opened by
"opendir". If used in list context, returns all the rest of
the entries in the directory. If there are no more entries,
returns an undefined value in scalar context or a null list in
list context.
If you're planning to filetest the return values out of a
"readdir", you'd better prepend the directory in question.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Otherwise, because we didn't "chdir" there, it would have been
testing the wrong file.
opendir(DIR, $some_dir) || die "can't opendir $some_dir: $!";
@dots = grep { /^\./ && -f "$some_dir/$_" } readdir(DIR);
closedir DIR;
John
--
use Perl;
program
fulfillment
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