Re: Count number of lines in a text file

[Anonymous Monk]

the sysread problem can be corrected with a fairly simple change - just check for the last buffer for the end of line. sample program showing some of the variations:

#
# demonstrate the sysread (and read) problem and correction.  we reall
+y only need a small
# file to demonstrate the problem....
#

use strict;

my $test_file="sysread_test_file.txt";       # change name to test siz
+e/length differences

#
# create the test file
#
sub create_test_file
{
    return if -e $test_file;               # we do not want to create 
+if it already exists....
    open TOUT,">$test_file";
    #
    # write a small file with an extra line missing the EOL.
    #
    for (my $line=0;$line<1000;$line++)
    {
        print TOUT "qwertyuiopasdfghjklzxcvbnm1234567890qwertyuiopasdf
+ghjklzxcvbnm1234567890qwertyuiopasdfghjklzxcvbnm1234567890\n";
    }
    print TOUT "qwertyuiopasdfghjklzxcvbnm1234567890qwertyuiopasdfghjk
+lzxcvbnm1234567890qwertyuiopasdfghjklzxcvbnm1234567890";      # no EO
+L!
    close TOUT;
}

sub test_while_variable
{
    my $linecount=0;
    open TIN,"<$test_file";
    while (<TIN>)
    {
        $linecount++;
    }
    close TIN;
    print "test_while_variable: $linecount\n";
}

sub test_block_read($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    binmode TIN;
    my ($data, $n);
    my $newlinecount=0;
    while ((read TIN, $data, $_[0]) != 0)
    {
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    print "test_block_read: $newlinecount\n";
}

sub test_fixed_block_read($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    binmode TIN;
    my ($data, $n);
    my $newlinecount=0;
    while ((read TIN, $data, $_[0]) != 0)
    {
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    $newlinecount++ if $data !~ /\012$/;
    print "test_fixed_block_read: $newlinecount\n";
}

sub test_block_sysread($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    my ($data, $n);
    my $newlinecount=0;
    while ((sysread TIN, $data, $_[0]) != 0)
    {
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    print "test_block_sysread: $newlinecount\n";
}

sub test_fixed_block_sysread($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    my ($data, $n);
    my $newlinecount=0;
    while ((sysread TIN, $data, $_[0]) != 0)
    {
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    $newlinecount++ if $data !~ /\012$/;
    print "test_fixed_block_sysread: $newlinecount\n";
}

#
# do the test
#

create_test_file;         # create the test file if not already presen
+t
test_while_variable;
test_block_read 4096;
test_fixed_block_read 4096;
test_block_sysread 4096;
test_fixed_block_sysread 4096;
exit 0;

[Anonymous Monk]

correction to the "fixed" routines in the demonstration code - it did not handle the "good" EOL case correctly because the "tr" removed the EOL and the original code thought the (good) EOL was missing as a result (I guess I learn something every day). this fix may not be perfect - I think it will return 1 for an empty file (untested) but I am sure there is a fix for that if someone really wants to do it.

I will not be offended if someone finds yet another problem (besides the empty file problem) and comes up with a solution. that is what this site is for - to help people do a better job writing Perl code and to teach people little things about Perl that they may not have known or thought much about.

sub test_fixed_block_read($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    binmode TIN;
    my ($data, $n);
    my $newlinecount=0;
    my $block_ends_with_eol=0;
    while ((read TIN, $data, $_[0]) != 0)
    {
        $block_ends_with_eol=1 if (substr $data,-1,1) eq "\n";
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    $newlinecount++ if (!$block_ends_with_eol);
    print ">>>test_fixed_block_read: $newlinecount\n";
}

sub test_fixed_block_sysread($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    my ($data, $n);
    my $newlinecount=0;
    my $block_ends_with_eol=0;
    while ((sysread TIN, $data, $_[0]) != 0)
    {
        $block_ends_with_eol=1 if (substr $data,-1,1) eq "\n";
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    $newlinecount++ if (!$block_ends_with_eol);
    print ">>>test_fixed_block_sysread: $newlinecount\n";
}