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

I usually run my perl scripts on an UNIX server, but recently I had to use a NT machine.

My script is very simple (or so I thought). I merely reads from a file and displays the info on the screen.

After copying the code from UNIX to NT it doesn't work.

This is a snippet of the script I am running.

-----------------------------------------------

open(DAT,"$FileName");
@inFile=<DAT>;
close(DAT);

print "$#inFile";
print "@inFile";

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After executing, the @inFile=<DAT> statement returns nothing and the $#inFile statement equals "-1".

$FileName points to a text file in the same directory as the script. There are no problems with opening or closing the file, just reading from it.

Can anyone help. It's probably very simple but it's got me stumped.

Cheers,

Scotty.

Replies are listed 'Best First'.
Re: Reading from a file on a NT server
by vek (Prior) on Jan 30, 2003 at 15:15 UTC
    Are you sure there are no problems with opening the file? You should always check the return value of open: 
    open(DAT, $fileName) || die "Could not open $fileName - $!\n";

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    Also bear in mind that you are slurping the entire file into an array which will be ok for small files but might present a memory problem if the files you are reading get larger. I would probably do something like this: 
    open(DAT, $fileName) || die "Could not open $fileName - $!\n";
while (<DAT>) {
   print $_, "\n";
}
close(DAT);

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    -- vek --
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Re: Reading from a file on a NT server
by perrin (Chancellor) on Jan 30, 2003 at 15:18 UTC
    How do you know there are no problems opening the file? You aren't checking for errors at all! Please perldoc perlopentut and learn about the use of $! for error reporting.
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      I am checking the return value of open() in my script. I removed this for simplicty when I asked for help. Below is my exact code for opening, reading and closing the file.

      $SaleFile="sales.csv";

# Print databases name
print "DATABASE FILE: $SaleFile<br>\n";

# Check to see if database exists
if (-e "$SaleFile"){print "FILE CHECK: $SaleFile does exist<br>\n"}els
+e{print "FILE CHECK: ERROR: $SaleFile does NOT exist<br>\n";}

# Open file for reading
if (open(DAT,"$SaleFile") <= 0){print "ERROR: $SaleFile can't be opene
+d<br>\n";}else{print "$SaleFile was opened successfully<br>\n";}

# Read from database
print <DAT>;
@inFile=<DAT>;

# Close database file
if (close(DAT) <= 0) {print "ERROR: $SaleFile can't be closed<br>\n";}
+else{print "$SaleFile was closed successfully<br>\n";}

print "DATABASE SIZE: $#inFile<br>\n";
print "DATABASE: @inFile<br>\n";

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      Cheers,

      Scotty

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[d/l]

        Ok, a few comments:

        • Asking for help with code and then giving people different code probably isn't going to help uncover problems with the actual code. If you're not going to submit the actual code, pare the actual code down until you have the smallest chunk that exhibits the problem you're seeing.
        • Checking for the existance of a file and then opening it creates a race condition. Not as much of a problem in this case, but it's a well known way to introduce bugs (or worse, security problems). Just open the file, and if it fails and you really want to know why check if $! was POSIX::ENOENT
        • The usual idiom is open(...) or die "Can't open foo: $!\n"; you're possibly betraying a C heritage, but remember Perl isn't C.
        • $#array is the index of the last element, not the size. You mean print "Size: ", scalar @inFile, "\n"
        • Putting ""'s around a single scalar variable (e.g. "$SaleFile") is pretty much useless (except in the case where the scalar contains a blessed object with a custom stringification routine, but that's not the case here).
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        ...
# Read from database
print <DAT>;
@inFile=<DAT>;

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        Erm ... you've already read the file and printed it to the screen. :-)

        Jenda

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