Perl Reference Card (Page 2 of 2) in pdf

Syntax:

Extended Constructs

8 One-Liners

(?#text)

escape

comment

-0

(zero) specify the input record separator

any single char

(?imxs-imsx:...)

enable or disable option

-a

split data into an array named @F

start of line

(?=...), (?!...)

positive / negative look-ahead

-F

specify pattern for -a to use when splitting

end of line

(?<=..), (?<!..)

positive / negative look-behind

-i

edit files in place

*, *?

0 or more times (greedy / nongreedy)

(?>...)

prohibit backtracking

-n

run through all the @ARGV arguments as files, using <>

+, +?

1 or more times (greedy / nongreedy)

(?{ code })

embedded code

-p

same as -n, but will also print the contents of $_

?, ??

0 or 1 times (greedy / nongreedy)

(??{ code })

dynamic regex

\b, \B

word boundary ( \w - \W) / match except at w.b.

(?(cond)yes|no)

condition corresponding to captured parentheses

Interactive Mode: perl -de 42

(?(cond)yes)

condition corresponding to look-around

string start (with /m)

Variables

string end (before \n)

Examples:

entire matched string

absolute string end

1. just lines 15 to 17, efficiently

everything prior to matched string

continue from previous m//g

perl -ne 'print if $. >= 15; exit if $. >= 17;'

everything after matched string

[...]

character set

2. just lines NOT between line 10 and 20

$1, $2 ...

n-th captured expression

(...)

group, capture to $1, $2

perl -ne 'print unless 10 .. 20'

last parenthesis pattern match

(?:...)

group without capturing

3. lines between START and END

$^N

most recently closed capt.

{n,m} , {n,m}?

at least n times, at most m times

perl -ne 'print if /^START$/ .. /^END$/'

$^R

result of last (?{...})

{n,}

, {n,}?

at least n times

4. in-place edit of *.c files changing all foo to bar

@-, @+

offsets of starts / ends of groups

{n}

, {n}?

exactly n times

perl -pi.bak -e 's/\bfoo\b/bar/g' *.c

5. delete first 10 lines

\1, \2

text from nth group ($1, ...)

perl -i.old -ne 'print unless 1 .. 10' foo.txt

Escape Sequences:

6. change all the isolated oldvar occurrences to newvar

7 Object-Oriented Perl and Modules

alarm (beep)

escape

perl -i.old -pe 's{\boldvar\b}{newvar}g' *.[chy]

formfeed

newline

7. printing each line in reverse order

Defining a new class:

carriage return

tab

perl -e 'print reverse <>' file1 file2 file3 ....

package Person;

\cx

control-x

lowercase next char

8. find palindromes in the /usr/dict/words dictionary file

use strict;

lowercase until \E

uppercase until \E

perl -lne '$_ = lc $_; print if $_ eq reverse'

sub new { #constructor, any name is fine

diable metachars until \E

end case modifications

/usr/dict/words

my $class = shift;

9. command-line that reverses all the bytes in a file

Character Classes:

my $self

= {};

perl -0777e 'print scalar reverse <>' f1 f2 f3

[amy]

'a', 'm', or 'y'

$self->{NAME} = undef; # field

10. word wrap between 50 and 72 chars

[f-j.-]

range f-j, dot, and dash

$self->{"_CENSUS"} = \$Census; # class data

perl -p000e 'tr/ \t\n\r/ /;

[^f-j]

everything except range f-j

++ ${ $self->{"_CENSUS"} };

s/(.{50,72})\s/$1\n/g;$_.="\n"x2'

\d, \D

digit [0-9] / non-digit

bless ($self, $class);

11. strip and remove double spaces

\w, \W

word char [a-zA-Z0-9_] / non-word

return $self;

perl -pe '$_ = " $_ "; tr/ \t/ /s; $_ =

char

}

substr($_,1,-1)'

\s, \S

whitepace [ \t\n\r\f] / non-space

sub name { #method

12. move '*.txt.out' to '*.out'

match a byte

my $self = shift;

perl -e '($n = $_) =~ s/\.txt(\.out)$/$1/ and not

\pP, \PP

match p-named unicode / non-p-named-unicode

if (@_) { $self->{NAME} = shift }

-e $n and rename $_, $n for @ARGV' *

\p{...}, \P{...}

match long-named unicode / non-named-unicode

return $self->{NAME};

match extended unicode

}

Posix:

sub DESTROY { #destructor

[:alnum]

alphanumeric

my $self = shift; -- ${$self->{"_CENSUS"} };}

[:alpha]

alphabetic

# so the ‘require’ or ‘use’ succeeds

[:ascii:]

any ASCII char

[:blank:]

whitespace [ \t]

Using the class:

[:cntrl:]

control characters

use Person;

[:digit:]

digits

$him = Person->new();

[:graph:]

alphanum + punctuation

$him->name("Jason");

[:lower:]

lowercase chars

printf "There's someone named %s.\n", $him->name;

[:print:]

alphanum, punct, space

use Data::Dumper; print Dumper($him); # debug

[:punct:]

punctuation

[:space:]

whitespace [\s\ck]

[:upper:]

uppercase chars

[:word:]

alphanum + '_'

[:xdigit:]

hex digit

[:^digit:]

non-digit

Installing Modules: perl -MCPAN -e shell;

Perl Reference Card Page 2

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