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FAQ 5.3 How do I count the number of lines in a file?
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FAQ 5.3 How do I count the number of lines in a file? PerlFAQ Server 03-05-2008
Posted by PerlFAQ Server on March 5, 2008, 9:03 pm
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 This is an excerpt from the latest version perlfaq5.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

--------------------------------------------------------------------

5.3: How do I count the number of lines in a file?


One fairly efficient way is to count newlines in the file. The following
program uses a feature of tr///, as documented in perlop. If your text
file doesn't end with a newline, then it's not really a proper text
file, so this may report one fewer line than you expect.

$lines = 0;
open(FILE, $filename) or die "Can't open `$filename': $!";
while (sysread FILE, $buffer, 4096) {
$lines += ($buffer =~ tr/\n//);
}
close FILE;

This assumes no funny games with newline translations.



--------------------------------------------------------------------

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are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
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perlfaq.pod.

Posted by jm on March 6, 2008, 5:11 pm
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 PerlFAQ Server a écrit :

> 5.3: How do I count the number of lines in a file?
>
>
> One fairly efficient way is to count newlines in the file. The following
> program uses a feature of tr///, as documented in perlop. If your text
> file doesn't end with a newline, then it's not really a proper text
> file, so this may report one fewer line than you expect.
>
> $lines = 0;
> open(FILE, $filename) or die "Can't open `$filename': $!";
> while (sysread FILE, $buffer, 4096) {
> $lines += ($buffer =~ tr/\n//);
> }
> close FILE;
>
> This assumes no funny games with newline translations.


How does this code handle other unicode new line codages, such as 0x85,
0x0d 0x0a?

Posted by brian d foy on March 7, 2008, 12:11 pm
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> PerlFAQ Server a écrit :
>
> > 5.3: How do I count the number of lines in a file?

> How does this code handle other unicode new line codages, such as 0x85,
> 0x0d 0x0a?

If you have a different idea of the human concept of "line", you'll
have to adjust the code to have the right line ending (and probably not
use tr///).

Posted by jm on March 7, 2008, 6:01 pm
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brian d foy a écrit :
>
>> PerlFAQ Server a écrit :
>>
>>> 5.3: How do I count the number of lines in a file?
>
>> How does this code handle other unicode new line codages, such as 0x85,
>> 0x0d 0x0a?
>
> If you have a different idea of the human concept of "line", you'll
> have to adjust the code to have the right line ending (and probably not
> use tr///).

I do not remember where I read it, but
specificity of computers standards is there are so many.


I assume the following can be used:

«A newline sequence is defined to be any of the following:

\u000A | \u000B | \u000C | \u000D | \u0085 | \u2028 | \u2029 |
\u000D\u000A »

This regular expression comes from:

http://www.unicode.org/unicode/reports/tr18/
Unicode Technical Standard #18
Unicode Regular Expressions

http://unicode.org/reports/tr13/tr13-9.html
Unicode Standard Annex #13
Unicode Newline Guidelines




However it is not always true, because with some encodings (cp850 for
instance), 0x85 is plain character.



PS: If I understand well, there is also a report which allow to
automagically display newlines when necessary according to
opportunities... but this is another issue.
http://www.unicode.org/reports/tr14/
Unicode Standard Annex #14
Line Breaking Properties

Posted by Peter J. Holzer on March 9, 2008, 9:28 am
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> brian d foy a écrit :
>>> PerlFAQ Server a écrit :
>>>
>>>> 5.3: How do I count the number of lines in a file?
>>
>>> How does this code handle other unicode new line codages, such as 0x85,
>>> 0x0d 0x0a?
>>
>> If you have a different idea of the human concept of "line", you'll
>> have to adjust the code to have the right line ending (and probably not
>> use tr///).

For perl, a newline is "\n". Conversion to and from some file encoding
should be done with the appropriate IO layer.


> I do not remember where I read it, but
> specificity of computers standards is there are so many.
>
>
> I assume the following can be used:
>
> «A newline sequence is defined to be any of the following:
>
> \u000A | \u000B | \u000C | \u000D | \u0085 | \u2028 | \u2029 |
> \u000D\u000A »

If all of these were just "newline sequences", they should be turned
into "\n" by the crlf conversion of the encoding(utf-*) layers. But they
aren't. For example, \u000C signifies not just a new line, but a new page.


> However it is not always true, because with some encodings (cp850 for
> instance), 0x85 is plain character.

cp850 doesn't have anything to do with unicode, so that doesn't seem
relevant.

        hp


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