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Perl_Notes.txt
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Perl_Notes.txt
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----------
perl Notes
----------
+---------------+
| documentation |
+---------------+
perldoc.perl.org
http://perldoc.perl.org/perlop.html # operators and precedence
http://perldoc.perl.org/perlfunc.html # functions
perldoc - Look up Perl documentation in Pod format
# perldoc -f print
cpan -a # create autobundle - list all modules installed
>>> Learning Perl: Bookmark: Chap 10. Exercises - pg. 188(188) <<<
# Get a list of all the encodings that perl understands
perl -MEncode -le "print for Encode->encodings(':all')"
perl -M"module" # execute/use module first
perldoc File::Spec File::Basename
+--------+
| pragma |
+--------+
use strict;
use feature "switch";
---
Installing/Building
- download the dist - unpack it - make it
MakeMaker
$ perl Makefile.PL [INSTALL_BASE=$HOME/lib]
$ make install
Module::Build
$ perl Build.PL [--install_base=$HOME/lib]
$ ./Build install
cpan "module to install"
---
use File::Basename qw/ /; # import no function (short) names
my $name = "/usr/local/bin/perl";
my $dirname = File::Basename::dirname $name;
-
use File::Spec;
my $new_name = File::Spec->catfile($dirname, $basename);
+-----------+
| operators |
+-----------+
chomp() # remove newline character
split() # break up a string according to a pattern
binmode() # use binary mode
select() # change STDOUT default
qw// # quick word(s)
m// # match
s/// # substitute
=~ # binding
my $likes_perl = (<STDIN> =~ /\byes\b/i);
$file_name =~ s#^.*/##s;
$copy =~ s/\d+ ribs?/10 ribs/;
(my $copy = $original) =~ s/\d+ ribs?/10 ribs/;
my $copy = $original =~ s/\d+ ribs?/10 ribs/r; # use 5.014;
+-----------+
| functions |
+-----------+
seek() # seek FILEHANDLE,POSITION,WHENCE (0|1|2)
# seek(TEST,0,1);
if {} elsif {} else {} - unless {}
expression ? if_true_expr : if_false_expr
my $average = $n ? ($total/$n) : "-----";
my $location = &is_weekend($day) ? "home" : "work";
my $size =
($width < 10) ? "small" :
($width < 20) ? "medium" :
($width < 50) ? "large" :
"extra-large"; # default
[LABEL:]while {} - until {}; last [LABEL], next, redo;
for () {} - foreach () {}; last, next, redo;
-----
| foreach (1..10) {
| print "Iteration number $_.\n\n";
| print "Please choose: last, next, redo, or none of the above? ";
| chomp(my $choice = <STDIN>);
| print "\n";
| last if $choice =~ /last/i;
| next if $choice =~ /next/i;
| redo if $choice =~ /redo/i;
| print "That wasn't any of the choices... onward!\n\n";
| }
| print "That's all, folks!\n";
-----
print "$n is a negative number.\n" if $n < 0;
&error("Invalid input") unless &valid($input);
$i *= 2 until $i > $j;
print " ", ($n += 2) while $n < 10;
&greet($_) foreach @person;
$x++; ++$x
$y--; --$y
for ($i = 1; $i <= 10; $i++) { # count from 1 to 10
print "I can count to $i!\n";
}
for (1..10) { # really a foreach loop from 1 to 10
print "I can count to $_!\n";
}
for ($_ = "bedrock"; s/(.)//; ) { # loops while the s/// is successful
print "One character is: $1\n";
}
+-----------+
| variables |
+-----------+
$_
$! # system error message
$| ($|=1) # force or always write to selected STUDOUT - do not buffer
$^I # create backup file with this extension
+-----------+
| RegEx |
+-----------+
/\p{Space}/ /\p{Digit}/ /\p{Hex}\p{Hex}/ # Unicode Properties
/\s/ /\d/ /\v/ /\t/ /\n/ /\f/
\w/a = [a-zA-Z0-9_]
[^\d] = [\D], [^\n] = [\N], /[\d\D]/
/HAL-[\d]+/a /HAL-[0-9]+/ /fred (and|or) barney/
/fred( +|\t+)barney/ /fred( |\t)+barney/
m{fred( +|\t+)barney} m%fred( |\t)+barney%
/y(....) d\1/ /y((.)(.)\3\2) d\1/ /(.)\g{1}11/ /(.)\g{–1}11/ /(.)(.)\g{–1}11/
---
. ? + .+? {n,m}? {n,}? ??
---
--- modifiers (can be combined) ---
/a (use ASCII) /u (use Unicode) /l (use locale)
/\d/a
/i (ignore case)
/yes/i
/m (turn no multi-line matching)
/s (have (.) match \n too, i.e. match any char)
/Barney.*Fred/s
/x (ignore literal space or tab within pattern) use \s or \t to match whitespace
/ -? [0-9]+ \.? [0-9]* /x # makes easier to read
if (m{
barney # the little guy
.* # anything in between
fred # the loud guy
}six) { # all three of /s and /i and /x
print "That string mentions Fred after Barney!\n";
}
--- anchors ---
\A (beginning of line) \z (end of line no \n) \Z (end of line w/\n)
m{\Ahttps?://}i m{\.png\z}i print if /\.png\Z/
/\A\s*\Z/ # match blank lines (with/without whitespace)
----------------------------------
if (s/\s+/ /g) { print "Successfully collapsed whitespace }
if (s/^\s+|\s+$//g) { print "Successfully removed leading|trailing whitespace }
--------------
m{\Ahttps?://}i
m{\.png\z}i
m{\.png\Z}i # optional \n at end
/\A\s*\Z/
/^barney/m
/fred$/m
/\bfred\b/ # word boundary - find only fred - not alfred or frederick
/\bhunt/ # find hunt, hunting, hunter - not shunt
/stone\b/ # find sandstone, flintstone - not capstones
/\bsearch\B/ # find searches, searching, searched - not search or researching
my $answered_yes = (<STDIN> =~ /\byes\b/i);
my $answered_yes = <STDIN> =~ /\byes\b/i;
if ($answered_yes) { };
(/(bronto)?saurus (steak|burger)/
(/(?:bronto)?saurus (steak|burger)/)
$names =~ m/(?<name1>\w+) (?:and|or) (?<name2>\w+)
I saw $+{name1} and $+{name2}
if ( $names =~ m/(?<last_name>\w+) and \w+ \g{last_name}/ )
if ("Hi there, bud" =~ /\s(\w+),/) {print "That was ($`)($&)($').\n"'}
if ("Hi there, bud" =~ /\s(\w+),/p) {print "That was(${^PREMATCH})(${^MATCH})(${^POSTMATCH}).\n";}
--------------
$_ = "I saw Barney with Fred.";
s/(fred|barney)/\U$1/gi; # $_ is now "I saw BARNEY with FRED."
s/(fred|barney)/\L$1/gi; # $_ is now "I saw barney with fred."
s/(\w+) with (\w+)/\U$2\E with $1/i; # $_ is now "I saw FRED with barney."
s/(fred|barney)/\u$1/ig; # $_ is now "I saw FRED with Barney."
s/(fred|barney)/\u\L$1/ig; # $_ is now "I saw Fred with Barney."
s#<BOLD>(.*?)</BOLD>#$1#g; # Fred and <BOLD>Velma</BOLD>, not <BOLD>Wilma</BOLD>
---
print "Hello, \L\u$name\E, would you like to play a game?\n";
----------------
@results = split /:/, "::ab:cd:efg::::", [-1];
@results = split /\s+/, $input_string;
split ' ', $string; # works on $string the same as just "split" on $_;
my($first, $second, $third) = /(\S+) (\S+), (\S+)/;
---
my $text = "Fred dropped a 5 ton granite block on Mr. Slate";
my @words = ($text =~ /([a-z]+)/ig);
---
my $data = "Barney Rubble Fred Flintstone Wilma Flintstone";
my %last_name = ($data =~ /(\w+)\s+(\w+)/g);
---
result = join $separator, @strings;
---
if ( (9 <= $hour) && ($hour < 17) ) {}
---
if ($dessert{'cake'} && $dessert{'ice cream'}) {
} elsif ($dessert{'cake'} || $dessert{'ice cream'}) {}
---
if ($dessert{'cake'} and $dessert{'ice cream'}) {
} elsif ($dessert{'cake'} or $dessert{'ice cream'}) {}
---
my $last_name = $last_name{$someone} || '(No last name)';
my $last_name = $last_name{$someone} // '(No last name)';
my $Verbose = $ENV{VERBOSE} // 1;
printf "%s", $name // '';
----------------------------------
perl -p -i.bak -w -e 's/Randall/Randal/g' fred*.dat
perl -e '
@fs = (
# filesystem & minimum free space needed (k)
["/eci/dev/sqr",32768],
["/eci/dev/sct",32768],
);
for $i (0..$#fs) {
$fs=$fs[$i][0];
$free=$fs[$i][1];
open(PIPE,"df -P \"$fs\" |") || die("pipe failed: $fs");
while(<PIPE>) {
chomp;
next unless (/\s$fs\s*$/);
@l = split(/\s+/);
$lv=$l[0];
$s=$l[1];
$f=$l[3];
$add=$free-$f;
if ($add > 0) {
$new=$s+$add;
print "# expand $fs\n";
print "lvextend -L ${new}k $lv && resize2fs $lv\n";
}
}
close(PIPE);
}
' >> $outputfile
-------------------------------------
hplog -v | perl -n -e 'if (/^\d\d\d\d\s/) { chomp; print "$_ "; $n=1; next; } if ($n)
{ print; $n=0; }' | grep -E 'Critical'
-------------------------------------
perl -p -i.bak -e 's/^\s*export\s*LD_ASSUME_KERNEL/#export LD_ASSUME_KERNEL/' /etc/galaxyprofile
( -p write/create a program, -i, set $^I to ".bak", -e execute)
-------------------------------------
$ perl -e 'printf("%d\n",0x5630c);'
353036
-------------------------------------
tags: perl