Re^3: Seperating individual lines of a file

Something that chargrill didn't mention, but might be an issue:

Doing a file open and file close for every line can get really expensive and time consuming if there happen to be thousands of lines of input.

Perl allows you to store file handles in a hash, so you can open a new file each time you see a new "hostname" string, and just re-use that handle whenever you see the same name again:

# set $listfile to some constant, or to $ARGV[0] (and supply the file 
+name
# as a command-line arg when you run the script)

my %outfh;  # hash to hold output file handles

open ORIGFILE, $listfile or die "$listfile: $!";
while ( <ORIGFILE> ) {
    my ( $host, $data ) = split " ", $_, 2;
    if ( ! exists( $outfh{$host} )) {
        open( $outfh{$host}, ">", $host ) or die "$host: $!";
    }
    print $outfh{$host} $data;
}
# perl will flush and close output files when done
[download]

Of course, if there are lots of different host names in the input file (or if there is something really wrong and unexpected in the list file contents), the script would die when it tries to open too many file handles.

Comment on Re^3: Seperating individual lines of a file Download Code

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Re^4: Seperating individual lines of a file by tgrossner (Novice) on Feb 03, 2006 at 16:25 UTC
I am trying out your code; I replaced the $listfile with $ARGV[0]. `#!/usr/bin/perl # set $listfile to some constant, or to $ARGV[0] (and supply the file #+name # as a command-line arg when you run the script) my %outfh; # hash to hold output file handles open ORIGFILE, $ARGV[0] or die "$ARGV[0]: $!"; while ( <ORIGFILE> ) { my ( $host, $data ) = split " ", $_, 2; if ( ! exists( $outfh{$host} )) { open( $outfh{$host}, ">", $host ) or die "$host: $!"; } print $outfh{$host} $data; } # perl will flush and close output files when done` [download] But this produces a syntax error of `Scalar found where operator expected at ./nocsplit.pl line 17, near "} + $data" (Missing operator before $data?) syntax error at ./nocsplit.pl line 17, near "} $data" Execution of ./nocsplit.pl aborted due to compilation errors.` [download] It seems to not like the `print to $outfh{$host} $data;` [download]	[reply] [d/l] [select]
Re^5: Seperating individual lines of a file by Not_a_Number (Prior) on Feb 03, 2006 at 20:14 UTC
There may be a more elegant solution, but graff's code works if you change the line: `print $outfh{$host} $data;` to: `my $fh = $outfh{$host}; print $fh $data;` [download] dave	[reply] [d/l] [select]
Re^5: Seperating individual lines of a file by blazar (Canon) on Feb 05, 2006 at 07:58 UTC
`print $outfh{$host} $data;` [download] In addition to Not_a_Number's solution by means of assigning to a temporary variable, another possible one is that given in perldoc -f print: `print { $outfh{$host} } $data;` [download]	[reply] [d/l] [select]