open file, write then read problem

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

hello, i have this code,

my $file1_temp = "output.txt";
open (FILE1_TEMP, "+>$file1_temp") or die "Could not open $file1_temp:
+ $!";
print FILE1_TEMP "hello, world!";
while (<FILE1_TEMP>) { print $_; }
close FILE1_TEMP;
[download]

but it prints nothing to the screen. Could somebody give an advice?

Thanks so much!
Donie

Comment on open file, write then read problem Download Code

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Re: open file, write then read problem by GrandFather (Saint) on Jun 15, 2009 at 00:35 UTC
We are good at giving advice. ;) First, always use strictures (quite likely you are in fact, but didn't include them in your sample). Use the three parameter version of open and use lexical file handles: `open my $FILE1_TEMP, '+>', $file1_temp or die "Could not open $file1_t +emp: $!";` [download] However, that is probably not the advice you want. Your code appends a string to a file then prints everything from the end of the file to, well, the end of the file - that is, nothing (as you have noticed). The fix is either to close and reopen the file, or to seek to the start before your while loop: `use strict; use warnings; my $file1_temp = "delme.txt"; open my $ioFile, '+>', $file1_temp or die "Could not open $file1_temp: + $!"; print $ioFile "hello, world!"; seek $ioFile, 0, 0; print while <$ioFile>; close $ioFile;` [download] True laziness is hard work	[reply] [d/l] [select]
Re^2: open file, write then read problem by doniking (Novice) on Jun 15, 2009 at 03:44 UTC
it works my ebook didn't explain about this pointer. Thanks, all. you save me. i'll be back	[reply]
Re: open file, write then read problem by Anonymous Monk on Jun 15, 2009 at 00:41 UTC
open the file handler for reading the file after u close the fh for writing. In your script the file pointer is pointing to new line hence is not printing any data open (FILE1_TEMP, "+>$file1_temp") or die "Could not open $file1_temp: $!"; print FILE1_TEMP "hello, world!"; close FILE1_TEMP; open (READFILE1_TEMP, "$file1_temp") or die "Could not open $file1_temp: $!"; while (<READFILE1_TEMP>) { print $_; } close READFILE1_TEMP;	[reply]