My Perl Notes

Usefull bits of Perl Code. I keep forgeting the syntax- hence this page..

Files

Strings

Associative Arrays

Files

Open Commands

open(OUT_FILE,">output.txt");    # Open for output (create)
open(OUT_FILE,">>output.txt");   # Open for output (append, or create)

Simple Read Loop

open(MY_FILE,"some.dat");
while( <MY_FILE> )
 {
 }

Printing to a file

open(OUT_FILE,">output.txt");    # Open for output (create)
print OUT_FILE "Hi There!\n";

Specifying File to open for input on the command line

open(MYFILE,$ARGV[0]) || die "can't open $ARGV[0]: $!\n"

Examining all files in a directory

require "find.pl";

&find('../some_directory');

sub wanted {
            #The "wanted" sub-rtn is called once for each file found, the file name
            # is passed in the $_ variable.
           }

Strings

String Concatenation

$string1 = "Hi " . "There!";

Testing if a string contains a sub string

if ($a_string =~ m/Elephant/)


To do a case insensitive search use- if ($a_string =~ m/Elephant/i)

Search, and Replace on a String

$a_string =~ s/Peking/Bejing/g;

Change String to all upper, or lower case

  $string =~ tr/a-z/A-Z/;  # convert to lower case
  $string =~ tr/A-Z/a-z/;  # convert to upper case

Finding First occurence of sub string in string

  $tmp_ptr = index($current_line,"something");

Grabbing a sub-string from a string

    $a_bit_of_string = substr($some_string,$start_pos,$length);

Splitting Strings by a character

$a_string= "name=john";
($tmp1, $tmp2) = split(/=/,$a_string);
#$tmp1 now has "name" in it, $tmp2 has "john"

Associative Arrays

Keeping a running count of the times a string is equal to a certain value
$different_strings{$a_string} = $different_strings{$a_string} + 1;
Looping thru an Associative Array, and examining each value
foreach (@some_assoc_array) { print $_; } # the value is in $_ by default
Looping thru an Associative Array, and assigning each key to a variable
foreach $variable_with_key (keys(%some_assoc_array)) { print $variable_with_key; }
Print the keys of a Associative Array in sorted order
@tmp_assoc_array_1 = keys(%some_assoc_array); @tmp_assoc_array_2 = sort @tmp_assoc_array_2; foreach (@tmp_assoc_array_2) ( print $_; }
Testing if a Associative Array has a key/value
if ($some_assoc_arry{$the_key} eq "" ) { print "key not in array"; }

IF Statement
IF statement
if ( $string eq "Hi There" ) if ( "A" gr "B" ) if ( $num == 10) if ( $num != 10) if ( $num > 10) if ($x > 208 && $x < 275 && $y > 64 && $y < 78 ) # && is AND, || is OR

Reports
Print a formatted print line-
#Define the Header Line format STDOUT_TOP= Name Address Num ----------- ---------------------- ----- . #Dot marks end of format #Define the detail Line format STDOUT = @<<<<<<<<<<<<<<<@<<<<<<<<<<<<<<<<<<<@###### $name, $address, $num, . #Dot marks end of format write; #Write the detail Line to STDOUT # Notes: < String Justify Left, > String Justify Right, | String Centered, # Numeric,

Subroutines
Calling Sub-rtn, and passing variables
&MY_SUB("John",1); #Call the sub-rtn, and pass it two literals sub MY_SUB { $name = $_[0]; $number = $_[1]; }

Misc Stuff
Executing shell commands
exec "pwd";
Reading whats in STDIN
if ($ENV{CONTENT_LENGTH} ne "") #** Is there anything in "Standard In" ? { read(STDIN, $save_string, $ENV{CONTENT_LENGTH}); # Yes- put it in $save_string }
Current System Date, and time
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time); $mon = $mon +1; $date_string = sprintf("%02d-%02d-%02d", $mon, $mday, $year); print "Date is ", $date_string; # prints mm-dd-yy

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