in reply to Re^2: First attempt at bringing in file for input/output
in thread First attempt at bringing in file for input/output

I liked your post++

To further clarify this and another thread having to do with while loop and $line=<filehande>:

#!usr/bin/perl
use strict;
use warnings;

while (my $line =<DATA> and $line !~ /^\s*$/)
{
    print "do somehing with non blank line\n";
}  

__END__
Value of <HANDLE> construct can be "0"; test with defined() at C:\User
+s\mmtho\Documents\PerlProjects\Monks\test_myVar_inwhile.pl line 5.
Global symbol "$line" requires explicit package name (did you forget t
+o declare "my $line"?) at C:\Users\mmtho\Documents\PerlProjects\Monks
+\test_myVar_inwhile.pl line 5.
Execution of C:\Users\mmtho\Documents\PerlProjects\Monks\test_myVar_in
+while.pl aborted due to compilation errors.

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To fix the first error message,... 
#!usr/bin/perl
use strict;
use warnings;


while (defined (my $line =<DATA>) and $line !~ /^\s*$/)
{
    print "do somehing with non blank line\n";
}  

__END__
Global symbol "$line" requires explicit package name (did you forget t
+o declare "my $line"?) at C:\Users\mmtho\Documents\PerlProjects\Monks
+\test_myVar_inwhile_ver2.pl line 6.
Execution of C:\Users\mmtho\Documents\PerlProjects\Monks\test_myVar_in
+while_ver2.pl aborted due to compilation errors.

[download]
Back up and fix just this error message...
#!usr/bin/perl
use strict;
use warnings;

my $line;

while ($line =<DATA> and $line !~ /^\s*$/)
{
    print "do somehing with non blank line\n";
}  

__END__
Value of <HANDLE> construct can be "0"; test with defined() at C:\User
+s\mmtho\Documents\PerlProjects\Monks\test_myVar_inwhile_ver2.pl line 
+7.
do somehing with non blank line
do somehing with non blank line

[download]
To make this work completely: 
#!usr/bin/perl
use strict;
use warnings;

my $line;

while (defined($line =<DATA>) and $line !~ /^\s*$/)
{
    print "do somehing with non blank line\n";
}  

__END__
do somehing with non blank line
do somehing with non blank line
do somehing with non blank line
do somehing with non blank line

[download]

Replies are listed 'Best First'.
Re^4: First attempt at bringing in file for input/output
by hippo (Archbishop) on Oct 24, 2018 at 08:43 UTC
    To make this work completely

    In such loops I prefer to limit the scope of $line but this might not concern you.

    #!usr/bin/perl
use strict;
use warnings;

while (my $line = <DATA>) {
    last unless $line =~ /\S/;
    print "Read: $line";
}

__DATA__
do a thing with non blank line
do a thing with non blank line
last one
  
no action on this line
nor this

    [download]
[reply]
[d/l]
[select]
      I prefer to put the main condition that "ends the loop" in the conditional.
      For a command line input, that might be detection of /(Q)uit/i or something like that.
      Other secondary conditions can go in the body of the loop.
[reply]
        but but but … isn't "end of <DATA>" the end-of-loop condition?

        reacting to a /Q(uit)?/i input is more or less just a convenience function, thus secondary :-)

[reply]
[d/l]

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