Counting Example

#!/usr/bin/perl -w
use strict;
use diagnostics;

print "\n";
print "+---------------------------------------------------------------+ \n";
print "| Count characters and/or words and/or lines in a file.         | \n";
print "+---------------------------------------------------------------+ \n\n";

#- 1 --------------------------------------------------------------------------
# Ask for filename
#------------------------------------------------------------------------------

print "File Name: ";                              # Display the question
my $TheFile = <stdin>;                            # Store what's typed in
chomp($TheFile);                                  # Get rid of line break

open(INFILE, $TheFile) or                         # Open the file if it exists
         die "The file $TheFile could not be found.  \n";

#- 2 --------------------------------------------------------------------------
# Do they want to count characters
#------------------------------------------------------------------------------
CHARQUESTION:

print "Count Characters? (y/n) ";                 # Display the question
my $CountChars = <stdin>;                         # Store what's typed in
chomp($CountChars);                               # Get rid of line break
$CountChars =& tr/A-Z/a-z/;                       # Change 'Y/N' to 'y/n'

    unless ($CountChars eq 'y' or 'n')            # If not 'y' or 'n', ask again
           {print "You must enter Y or N. \n";
            goto WORDQUESTION;
           }    
my $CharCount = 0;                                # Initialize the counter

#- 3 --------------------------------------------------------------------------
# Do they want to count words?
#------------------------------------------------------------------------------
WORDQUESTION:

print "Count Words? (y/n)      ";                 # Display the question
my $CountWords = <stdin>;                         # Store what's typed in
chomp($CountWords);                               # Get rid of line break
$CountWords =& tr/A-Z/a-z/;                       # Change 'Y/N' to 'y/n'

    unless ($CountWords eq 'y' or 'n')            # If not 'y' or 'n', ask again
           {print "You must enter Y or N. \n";
            goto WORDQUESTION;
           }    
my $WordCount = 0;                                # Initialize the counter
   
#- 4 --------------------------------------------------------------------------
# Do they want to count lines? (records)
#------------------------------------------------------------------------------
LINEQUESTION:

print "Count Lines? (y/n)      ";                 # Display the question
my $CountLines = <stdin>;                         # Store what's typed in
chomp($CountLines);                               # Get rid of line break
$CountLines =& tr/A-Z/a-z/;                       # Change 'Y/N' to 'y/n'

    unless ($CountLines eq 'y' or 'n')            # If not 'y' or 'n', ask again
           {print "You must enter Y or N. \n";
            goto LINEQUESTION;
           }    
my $LineCount = 0;                                # Initialize the counter

#- 5 --------------------------------------------------------------------------
# While there are records in the file...
#-----------------------------------------------------------------------------
while(<infile>)
{ my $TheLine = $_;                               # Save the line's contents
  $LineCount = $LineCount + 1;                    # Count Lines

  #----------------------------------------------------------------------------
  # count characters
  #----------------------------------------------------------------------------
  chomp($TheLine);                                # Get rid of the line break
  if($TheLine eq "") { next };                    # If line blank, get the next
  my $LineLen   = length($TheLine);               # Get line length
  $CharCount = $CharCount + $LineLen;             # increment char count
  $WordCount = $WordCount + 1;                    # This line has at least 1 word

  #---------------------------------------------------------------------------
  # Now loop through each character on this line to look for words
  #----------------------------------------------------------------------------
  my $CharPos = 0;                                # Position we are in the line

  until($CharPos == $LineLen)                     # Check for line end;
     {if(substr($TheLine, $CharPos, 1) eq " ")    #   if not, check for space
     { $WordCount = $WordCount + 1 }
       $CharPos = $CharPos + 1;
     }                                            # End of until
}                                                 # End of while(<infile>) loop
#- 6 --------------------------------------------------------------------------
# Write A Small Sub Routine To Do The Same (from wondersky.com)
#------------------------------------------------------------------------------
sub comma_me {
              local $_ = shift;
              1 while s/^(-?\d+)(\d{3})/$1,$2/;
              return $_;
             }
#------------------------------------------------------------------------------
# All finished, so print out the results
#------------------------------------------------------------------------------

print "\n";
print "************************************* \n";
print "* $0 COMPLETED SUCCESSFULLY           \n";
print "************************************* \n\n";
print "Counts For $TheFile: \n\n";

if ($CountChars eq "y")
                {print "Number of characters: ", comma_me($CharCount), "\n"};
if ($CountWords eq "y")
                {print "Number of words     : ", comma_me($WordCount), "\n"};
if ($CountLines eq "y")
                {print "Number of lines     : ", comma_me($LineCount), "\n"};
                 print "\n";

Miscellaneous Notes

perl -v
the version of perl running
(most recent from www.activestate.com)
perl -c
check syntax but don't run
perl -w
check program more thoroughly than -c
perl -e "code;"
run one line program
perl -i
use perl to edit files
perl -d 
perl's debugger
#!/usr/bin/perl -w
first line in code on Unix
Variable Names: Case-sensitive. Any Length. A-z and Underscores. Can't start with a number.

#

comment -- starts anywhere on the line
=

set value on left to value on right
;

statement end.
not required at the end of a block.
{}

beginning and end of block. can be embedded. 
.
open(INFILE,$TheFile)
or die "The file $TheFile could ".
    "not be found. \n";
concatenation
+
$variable = $variable + 1;
add values on right
and store in variable on the left
$0

the name of the program that is running
$_
$TheLine = $_;
Save the line's contents
\n

line break
++
$LineCount++; 
Increment value
/t

tab
hex

\x42 = B
octal

\102 = B
chr
$CapB = chr(66);

STDIN
my $SearchValue = <STDIN>; 
What user has typed 
tr
$DoSearch =~ tr/A-Z/a-z/;
translate value to lowercase
print
print "some text and $variable \n";

length
$varLength = length($variable2);

open
open(filehandle,$filename)
or die("message to display if not found \n");
Open file. If not able, post message
substr
$var = substr($Line,$PosFromZero,$Len);
substring
chomp
chomp($TheLine);
get rid of the line break
seek
seek(INDB,0,0);
Tells Perl where in the file to start
split
($Var1, $Var2) = split(/\t/, $TheRec);
split a string based on a
value into separate variables
While Loop
while()             # while there are records in the file
{ $TheLine = $_;    # save the line's contents
  chomp($TheLine);  # get rid of the line break

  if($TheLine = "")
     {next};        # don't count if the line is a blank
     $LineCount++;  # increment the line count
};                  # end of block

while(1)            # loop forever (1=true)
{ print "Y or N";   # show this line on the screen.
  my $Search = ;    # save what's typed
};                  # end of block
Until Loop
until ($var1 == $var2)
{ if ($var3 eq $var4)
   { do some statements }
 }
If 
if ($variable eq "value")
     {block of statements};
     if ($TheLine = "")
         {next} ;   # don't count if the line is a blank
     if ($Cntr == 0)
         {print "zero"};
Unless
unless($DoSearch eq 'i')     # If not 'i',
    { print "Enter I or Q.\n";
      next;                  # Go back to 'while' for next try
    }
For
for ($i = 33;
     $i <=126;
     $i++)
           {statements}
Last
if($SrchVal eq 'q') {last}
Next
if($TheLine = "") {next}; 


' vs "
'do not interpret (except for ' and \)
"interprets

print 'Lynn\'s programs are on usr\\user\\ltobias.';
Lynn's programs are on usr\user\ltobias.

$Shout = "Help!";
print "Please come when I shout \"$Shout\". \n";
Please come when I shout "Help!". 

$Value = "something";
print "\$Value is $Value. \n";
$Value is something.