Pro Perl

Pro Perl

Peter Wainwright

Language: English

Pages: 1064

ISBN: 159059438X

Format: PDF / Kindle (mobi) / ePub

*Condensed, readable style; delivers tremendous value in just one book. This book offers *THE resource for focused and pragmatic industrial solutions in Perl, while the competing *best-sellers are older, quirkier and shallower treatments of Perl.

*Thorough discussion of Perl―from installations to applications development; ideal for working Perl programmers in 2005.

*Wainwright is a respected Perl expert and author of industry-respected Pro Apache title.

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Conventional unless (open FILE, $filename) { die "Cannot open file: $!"; } We can also provide a list of statements (separated by commas) or a do block for the condition to execute on success. Here is an example that supplies a list: open (FILE, $filename) or print (LOG "$filename failed: $!"), die "Cannot open file:$!"; Not every programmer likes using commas to separate statements, so we can instead use a do block. This also avoids the need to use parentheses to delineate the arguments to.

/usr/local/lib/perl5/5.8.5 /usr/local/lib/perl5/site_perl/5.8.5/i686-linux-thread-multi /usr/local/lib/perl5/site_perl/5.8.5 /usr/local/lib/perl5/site_perl . > Likewise, the following example prints the value of the environment variable PATH. While the variable is a hash, the values in the hash are scalars, so the correct prefix to retrieve it is $: > perl -e 'print $ENV{PATH}' /usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin> Variables like %ENV and @ARGV, which hold the command-line arguments with.

Get four characters from the first string value, whereas 'aaaa' will get one each from the first, second, third, and fourth. print print print # pack 'aaaa', 'First','Second','Third','Fourth'; # produces pack 'a4', 'First','Second','Third','Fourth'; # produces pack 'a4a4a4a4', 'First','Second','Third','Fourth'; produces 'FirsSecoThirFour' 'FSTF' 'Firs' From Perl 5.8 pack and unpack can also use parentheses to group repeating sequences of template characters. To represent four integers, each.

Larger range of cases. In some very special cases—typically where the same values appear many times in the list to be sorted—it might be more efficient to switch to the older algorithm. To do this, use use sort _quicksort; To reinstate the newer mergesort: use sort _mergesort; In the vast majority of cases, the distinction between these two algorithms is close to undetectable and will only be of interest to programmers who are critically concerned with performance and have datasets with many.

Contains data, we get a string containing a numeric ratio of the form N/M that describes in approximate terms how efficiently Perl has been able to store the keys and values in the hash. Loosely speaking, the numbers are a ratio and can be read as a fraction, the higher the first relative to the second, the more efficient the storage of the hash. #!/usr/bin/perl # use warnings; use strict; my %hash = (one => 1, two => 2, three => 3, four => 4, five => 5); # check the hash has data if.

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