Hello robby_dobby,

You make many good points. I would add:

• Prefer chomp to chop when removing a terminal newline, as it’s safer.

But I find this comment a bit strange:

I see this convention of if(open($filehandle, "filename") || die $!) - this is really odd style. This means that whatever happens, straight or exceptional flow, go ahead an process this file.

Of course, the if is entirely redundant here. But surely, if the code throws an exception (i.e., die is called), the file will never be processed?

17:11 >perl -Mstrict -wE "say 'Ok 1'; if (open(my $fh, 'nonexistent.tx
+t') || die $!) { say 'Ok 2'; } say 'Ok 3';"
Ok 1
No such file or directory at -e line 1.

17:11 >
[download]

Or have I misunderstood what you’re saying?

for the OP might be worth only add few words about || and or: the high precedence || is valid and right as we put parens, without parens has another effect:


use strict; 
use warnings;

open my $fh, '<', 'notexistant.txt' or die qq(File open failed);   #OK
+:     File open failed at

open (my $fh, '<', 'notexistant.txt') || die qq(File open failed); #OK
+ too: File open failed at..

open my $fh, '<', 'notexistant.txt' || die qq(File open failed);   #WR
+ONG 
print  <$fh>;                                                      # r
+eadline() on closed filehandle $fh at..
[download]

Just think of "and" and "or" as being the same as && and ||, but so low on the precedence chart that parenthesis are usually unnecessary to keep the things on the left or on the right properly grouped. It is almost always considered better to use "or" instead of "||" when you work with open.

is a quote from a a very useful post about idioms and precedences: Perl Idioms Explained - && and || "Short Circuit" operators

L*

There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

Hello Athanasius,

No, you're completely right. I got distracted as I was typing this - this should remind me not to post when doing something. :-)

Still, it stood out to me as weird that he relied on open's return value to check for success.

hello sir i have enclosed with please see

Hello,

I have updated my post here.

hii robby_dobby thanks for the suggestion. have applied those and the code is working without any warnings, but its not producing the output as desired. in the code i have opened config.txt, where you have suggested changes, in config file i have written chipid 1925 subversid 0001 and want only to read numeric value and use them but the code is picking only chipid string and using it. please tell me how should i write the code so that only numeric value is picked from config file please fine the code portion below

if(open (my $CFILE,"config.txt" ) || die "couldnt open file:", $! ) {
   $readline = <$CFILE>;
   if (defined $readline ) {
        @words = split(/\b[0-9][0-9][0-9][0-9]\b/,$readline);
        $readline = <$CFILE>;
      }
   $cChipId = $words[0];
   $cSubVersId = $words[1];
   print "$cChipId \n";
   print "$cSubVersId \n";
}
[download]

Hello mrityunjaynath,

If you say split(/X/, $string), then $string is split into chunks separated by whatever is matched by X. For example, in this one-liner:

18:05 >perl -MData::Dump -wE "my $s = 'Hello1234world!5678How9012are34
+56you?'; my @w = split /[0-9]{4}/, $s; dd \@w;"
["Hello", "world!", "How", "are", "you?"]

18:06 >
[download]

the string is split on 4-digit groups, and the array @w is populated with the words in $s which come between those digits.

To capture the digit groups, you could try to split on non-digits, but it’s much better (and more straightforward) to use a regular expression with a /g modifier, like this:

open(my $CFILE, '<', 'config.txt') or die "Couldn't open file 'config.
+txt' for reading: $!";
$readline = <$CFILE>;
@words = $readline =~ /([0-9]{4})/g;
[download]

as demonstrated in this one-liner:

18:06 >perl -MData::Dump -wE "my $s = 'Hello1234world!5678How9012are34
+56you?'; my @w = $s =~ /([0-9]{4})/g; dd \@w;"
[1234, 5678, 9012, 3456]

18:18 >
[download]

See split and perlretut.

Hope that helps,

Athanasius <°(((>< contra mundum

Iustus alius egestas vitae, eros Piratica,

hii athanasius i have tried something on the above code . its working but when i have printed $chipID it prints cChipId and $cSubVersId gives 1925 (in last two lines of code ) while the value i have provided through config text ChipId 1925 and SubVersId 0003. so its problemetic output. no warning this time though

my @words;
my $readline;
my $cChipId;
my $cSubVersId;
if(open (my $CFILE,"config.txt" ) || die "couldnt open file:", $! ) {
   $readline = <$CFILE>;
    chop($readline);
   if (defined $readline ) {
        @words = split(/ /,$readline);
        $readline = <$CFILE>;
        chop($readline);
      }
   $cChipId = $words[0];
   $cSubVersId = $words[1];
   print "$cChipId \n";
   print "$cSubVersId \n";
}
[download]

thanks

Hello,

Athanasius mentions a good point about using chomp instead of chop. I haven't completely looked at your code when I spotted those few errors.

If others haven't got around to it before then, I'll reply back to you when I find the time.