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

Dear all Mighty Monks,
Is that any script reference that can check whether a file exist in a folder. Then if the file is not exist it will return something. So that I will know the files is not there. Because the way I code it is very back and slow some more got bugs. For a beginner like me in perl need to learn lot now.
Thank you.
  • Comment on Is any any script checking File Existance

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Re: Is any any script checking File Existance
by rob_au (Abbot) on Oct 11, 2002 at 04:08 UTC
    The previous posts have pointed you in the right direction with regard to your question and file test operators. I would only add some additional information about a lesser known module included with the core Perl distribution which may also be of use if testing for the existence of a large number of files.

    The File::CheckTree module can be used to perform file tests on a large number of files within a directory tree. For example, from the documentation for this module:

    use File::CheckTree;

$warnings += validate( q{
    /vmunix                 -e || die
    /boot                   -e || die
    /bin                    cd
        csh                 -ex
        csh                 !-ug
        sh                  -ex
        sh                  !-ug
    /usr                    -d || warn "What happened to $file?\n"
});

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    The real power of this module however lies in the ability to perform a great number of file tests, moreso than existence (-e) checks, on a large group of files as the example above demonstrates.

     

    perl -e 'print+unpack("N",pack("B32","00000000000000000000000111001110")),"\n"'

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Re: Is any any script checking File Existance
by Enlil (Parson) on Oct 11, 2002 at 03:19 UTC
    Try this: 
    my $file_name = "some_file_name";

if ( -e $file_name ) { DO_STUFF }

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    the -e checks for the existance of a file and returns true or false so if it does not exist it will not go into the if loop. I think this is what you are asking.

    _Enlil_

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Re: Is any any script checking File Existance
by tadman (Prior) on Oct 11, 2002 at 06:19 UTC
    There is a section in perlfunc that explains the file test functions: 
                       -e  File exists.
                   -z  File has zero size (is empty).
                   -s  File has nonzero size (returns size in bytes).

                   -f  File is a plain file.
                   -d  File is a directory.

                   -T  File is an ASCII text file.
                   -B  File is a "binary" file (opposite of -T).

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    You can use any of these to test for the presence of a file, depending on your exact requirements. For example: 
    if (-f $my_file)
{
     print "Thanks for not deleting my config file $my_file\n";
}
if (-B $my_file || -z $my_file)
{
     print "I'll bet you think you're funny.\n";
}

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    They look odd, I know, functions that start with dashes are a teeny bit unusual, but then again, regular expressions are far stranger.

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Re: Is any any script checking File Existance
by rbc (Curate) on Oct 11, 2002 at 03:32 UTC
    you can also read about a bunch of "file test" stuff by doing ... 
    $ perldoc -f-e

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