Perl

for loops
OOP
Files
List Array
subroutines
Hashes
Strings
Regular Expressions
Programs
Command Line Perl

Programs

p029.pl   p028.pl   p027.pl   p026.pl   p025.pl   p024.pl   p023.pl   p022.pl   p021.pl   p020.pl   p019.pl   p018.pl   p017.pl   p016.pl   p015.pl   p014.pl   p013.pl   p012.pl   p011.pl   p010.pl   p009.pl   p008.pl   p007.pl   p006.pl   p005.pl   p004.pl   p003.pl   p002.pl   p001.pl  

OOP Application

CI implementation
In ~/base/p1/misc/proj/script/
update_report_html.pl   test01.pl   test02.pl   test03.pl   ProjReport.pm   ReportHtml.pm  

For good code
use warnings;
use strict;
further
use diagnostics;

command line
foreach $arg (0 .. $#ARGV)
  { printf "*%s*\n",$ARGV[$arg]; }

List Array

$self->{'processed'}=(); - new list in class variable
my $current = shift(@{$self->{'processqueue'}}); - shift deletes from the start
pop deletes from end
unshift @names, "Frank" - adds Frank to the start
push @names, "Chelton"
adds to end
$#list size of list-1
scalar @arraysize of list
if (defined(@{$self->{'errorunknownfiles'}})) - can not ask the size of an array if no elements in it!
my @p3=(@p1,@p2) joining lists.
my @p4=@p3 assignment
@{p3}[2] access
splice @names,1,3; cuts from pos 1, 3 elements.

my $s1="a:b:c";
my @a2 = split(/:/,$s1);
my @a3 = split /\s+/,$s1 on space

Array of arrays
my @A =
(
  ["0","1","2","3"],
  ["4","5","6","7"]
);
print $A[1][3];
Using references
my @v2 = (1,3,5,7,'eleven');
my $rv2 = \@v2;
$rv2->[4]=11;
print "@v2";
Array of references
my @v3 = (2,4,6,8,10);
my $rv3 = \@v3;
my @m1 = ($rv2,$rv3);

For OOP
$self->{'data'}=();
build by pushing array
push(@{$self->{'data'}},\@arr);
Now iterating over it
for(my $i=0; $i <= $#{$self->{'data'}}; $i++)
  foreach(@{$self->{'data'}[$i]})


if ( ! defined($x1) ) ... testing for undefined variables.

Files

rename($old,$new);

open for writing   p011.pl
exercise: open a file for writing and print with right justification, implements trim function   p012.pl
Reading and testing p007.pl

< for read, > for write.
open FILE, ">filename.txt" or die $!;
my @lines = <FILE>;
close(FILE);
foreach(@lines) { ... }


Find p010.pl Misc.pm p022.pl

if (-e $filename) { ... } file exists

symlink   p008.pl

Perldoc

$ perldoc strict
$ perldoc -f substr

Subroutines

My convention for arguments and return value
# 1: first arg
# 2: second arg
# ...
# Return a ...
sub somefunc
{
  my $arg1_=shift; ...
See p013.pl

Passing arrays p019.pl
Passing hashes p018.pl

OOP

Implemented basic OOP.

Inheritance and virtual functions
p016/main.pl   p016/Fruit.pm   p016/Apple.pm  

This required each class to have its own file, which means each program now needs its own directory as programs generally have several classes.
i.e. <class name>.pm

p017.pl - looks as separating access from modifying variables, perhaps more trouble than its worth.

Composition
p014/main.pl   p014/GeomPoint.pm   p014/GeomCircle.pm  

Accessing list from hash inside the class
foreach (@{$self->{'report'}})
  { printf "*%s",$_; };

use lib "../p1/comsci/pl" adds to @INC, then use a package there
use MyTimestamp; require "path/file.pm"; does a specific file

Hashes

Define and access
my %wk =
(
  "Jan", "01",
  "Feb", "02",
...
);
my $mon2 = %wkday->{"Mar"};


exists, delete p020.pl

hash from list
my $h1=( "Fred", 84893, "Pete", 9630 );
\%h1 pass to subroutine
$h1{"Hawaii"}=32854; add
for loop in sub
my $h2=shift;
my $key;
foreach $key (sort %$h2)
{ printf "%s : %d\n",$key,$h2{$key}; }
See p018.pl

Strings

my $s1="hat"; a string
my $len=length($s1) string length
if ($s1 eq "hat") { ... } string comparison
ne string not equal
my $s2 = $s1 . "abc"; add strings
{eq,ne,gt,lt,ge,le}

my $s2=substr($s1,1,-1); delete first and last characters
substr($s1, index($s1,'float25'),7) = 'float50'; replace a string inside $s1

Regular Expressions

$_ is the global variable for the pattern.
  $_="Some test string";
if ($s1=~/pattern/)... $s1 is target string
$` start
$& what matched
$' end

.* matches everything
/pat1.*pat2/s include new lines
/^\s*$/ blank line
\d+ at least one digit
-? optional -
/true/i case insensitive
\b beginning or end match of word
/\bcat\b/ matches word cat only
/^The/ start matched
/end.$/ end of string

Match lines, see p026.pl
my @out = grep { /\Q$line\E/} @lines;
Negative of a search with ! operator
my @a3 = grep {!/proj\/html/} @files;
if (! /proj\/html/) ...

Modules

Perl Slurp Module

Command Line Perl

More difficult to write but works.

To use perl to return error codes to the os.
my $file="tmp12.txt";
if ( -e $file )
{ unlink $file; exit(0); } exit(1);