Re: How to set as record separator in a Perl one liner?

2012-07-16 Thread Michael Brader 

On 07/16/2012 04:05 PM, De-Jian Zhao wrote:

Hi,

I want to change the record separator in a Perl one liner with  as the 
separator. However, I tried without success.


The perlrun document 
(http://perldoc.perl.org/perlrun.html#Command-Switches) says that*
***-0*[/octal/hexadecimal/] * specifies the input record separator (|$/| 
) as an octal or hexadecimal number. *
*When I tried to get the octal/hexadecimal code of  with oct() and 
hex(), I got 0. I used this number and it did not work the way I 
wanted (perl -00 -ne 'print if //' test.seq ).




From 'perldoc -f oct'

...
oct Interprets EXPR as an octal string and returns the corresponding
value.
...
To go the other way (produce a
number in octal), use sprintf() or printf():

$perms = (stat(filename))[2]  0;
$oct_perms = sprintf %lo, $perms;

So it is used for converting a string into an octal value. But we can go 
the other way with printf and ord:


perl -e 'printf %lo\n, ord(q{})'
76

Now perl will leave the input record separator on the string, but we can 
take that off with chop:


echo '' | perl -0076 -nE 'chop,say if //'


TIMTOWTDI of course, and you could also do it like this:

echo '' | perl -nE 'for (split //) { say if // }'


Cheers,
Michael


Do the functions (oct and hex) return the octal and hexadecimal value of 
the inputted character? The document on the web seems to give different 
answers.


http://perldoc.perl.org/index-functions-by-cat.html#Functions-for-SCALARs-or-strings 

hex http://perldoc.perl.org/functions/hex.html - convert a string to a 
hexadecimal number
oct http://perldoc.perl.org/functions/oct.html - convert a string to an 
octal number


http://perldoc.perl.org/functions/hex.html
*hex EXPR **hex* Interprets EXPR as a hex string and returns the 
corresponding value.


http://perldoc.perl.org/functions/oct.html
*oct EXPR **oct* Interprets EXPR as an octal string and returns the 
corresponding value.


I tested the functions. The first description is possibly wrong. If I am 
right, which functions could be used to get the octal and hexadecimal 
number of a string? How should the Perl one liner be written to change 
the record sepatator to ? Thanks for your attention.


Dejian




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  Technology/Softdev/ME Small Change Team
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Re: How to set as record separator in a Perl one liner?

2012-07-16 Thread Shlomi Fish 
Hi Dejian,

On Mon, 16 Jul 2012 14:35:33 +0800
De-Jian Zhao dejian.z...@gmail.com wrote:

 Hi,
 
 I want to change the record separator in a Perl one liner with  as 
 the separator. However, I tried without success.
 
 The perlrun document 
 (http://perldoc.perl.org/perlrun.html#Command-Switches) says that*
 ***-0*[/octal/hexadecimal/] * specifies the input record separator 
 (|$/| ) as an octal or hexadecimal number. *
 *When I tried to get the octal/hexadecimal code of  with oct() and 
 hex(), I got 0. I used this number and it did not work the way I 
 wanted (perl -00 -ne 'print if //' test.seq ).

You need to do sprintf(%o, ord()) instead:

$ perl -E 'say sprintf(%o, ord())'
76

oct and hex convert FROM octal or hexadecimal. sprintf(%o) converts TO octal.
And  is a string, and you need http://perldoc.perl.org/functions/ord.html to
return its first character's numeric value.

Regards,

Shlomi Fish

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Re: How to set as record separator in a Perl one liner?

2012-07-16 Thread John W. Krahn 

Michael Brader wrote:

On 07/16/2012 04:05 PM, De-Jian Zhao wrote:


I want to change the record separator in a Perl one liner with  as
the separator. However, I tried without success.

The perlrun document
(http://perldoc.perl.org/perlrun.html#Command-Switches) says that*
***-0*[/octal/hexadecimal/] * specifies the input record separator
(|$/| ) as an octal or hexadecimal number. *
*When I tried to get the octal/hexadecimal code of  with oct()
and hex(), I got 0. I used this number and it did not work the
way I wanted (perl -00 -ne 'print if //' test.seq ).



 From 'perldoc -f oct'

...
oct Interprets EXPR as an octal string and returns the corresponding
value.
...
To go the other way (produce a
number in octal), use sprintf() or printf():

$perms = (stat(filename))[2]  0;
$oct_perms = sprintf %lo, $perms;

So it is used for converting a string into an octal value. But we can go
the other way with printf and ord:

perl -e 'printf %lo\n, ord(q{})'
76

Now perl will leave the input record separator on the string, but we can
take that off with chop:

echo '' | perl -0076 -nE 'chop,say if //'



Better to use chomp (the -l switch) instead of chop:

echo '' | perl -0076nlE 'say if //'



TIMTOWTDI of course, and you could also do it like this:

echo '' | perl -nE 'for (split //) { say if // }'



echo '' | perl -F -naE '//  say for @F'

:-)



John
--
Any intelligent fool can make things bigger and
more complex... It takes a touch of genius -
and a lot of courage to move in the opposite
direction.   -- Albert Einstein

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