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Perl program code for freq.pl

This file contains the actual Perl code for freq.pl. The program assumes lines of data, all the same length, with information you want to count in the same columns all through the file. That's called an LRECL (logical record length) file.

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#!/usr/bin/perl -w
##---------------------------------------------------------------------------##
##  File:
##      @(#)  freq.pl 1.0 97/05/13 @(#)
##  Author:
##      Kent Nassen     knassen@umich.edu
##  Description:
##      A script for grabbing quick and dirty frequencies
##      from an LRECL data file (vars in fixed column locations)
##
##  Usage:
##      freq.pl [-h] [-c[#-#][#] filename]
##   where: -c#-# indicates starting & ending column numbers of the variable
##          and -c# indicates a single-column variable at column #.
##      
##---------------------------------------------------------------------------##

use Getopt::Std; # use getopt module to parse the command line
$opt_h="";

# Get our name without a path
($ProgName = $0) =~ s%.*/%%;

# Usage message subroutine
sub DisplayUsage {
    print "\nUsage: $ProgName [-h] [-c[#-#][#] filename]\n",
	  "       -c#-#      Start-End column numbers of variable\n",
	  "       -c#        Single column variable at column #\n",
  	  "       filename   LRECL data file filename\n",
	  "       -h         Show this help screen\n",
	  "\n",
	  "       Example: $ProgName -c5-7 fylename.dat\n",
	  "\n       (Column numbers in the file start at column 1)\n\n";
      exit 0;  # all calls to DisplayUsage exit with error code 0...not good
}   # end DisplayUsage

# Get possible options (-c requires a parameter)
getopts (('hc:') || &DisplayUsage); 
&DisplayUsage if ($opt_h);

# Parse the -c option for starting and ending column locations
# (ending location may not be present if the variable is only
# one column wide)
# Note if -c option ends with a hyphen, that will be interpreted as
# another option (filename) since hyphens start options.
if (!$opt_c) { print "\nI need column locations!\n"; 
			&DisplayUsage;
			} # if we don't have an opt_c, no need to go further
$_ = $opt_c;
if (/^([0-9]+)-([0-9]+$)/) { # both starting and ending locations: #-#
	$startcol=$1;
	$endcol=$2;
	}
elsif (/^[0-9]+$/) { # just starting location: #
	$startcol=$opt_c;
	$endcol=$startcol;
	}
else { print "\nI couldn't understand your column location(s)!\n"; 
	&DisplayUsage;
	}

# See if the column locations of the variable make sense
if ($endcol==0 || $startcol==0) {
	print "\nStarting or ending column was zero.\n";
	&DisplayUsage;
	}

# Assume startcol > endcol is a transposition of column locations
# You may want to make this an error instead.
#if ($startcol > $endcol) { # swap startcol and endcol
#	$temp=$endcol; 
#	$endcol=$startcol; 
#	$startcol=$temp; 
#	}

# Set up a string var for printing out hyphenated column locations 
$loc="$startcol"."-"."$endcol";

# What is left on the command is the filename to be processed (hopefully)
if ($#ARGV>0) { print "\nOne filename at a time, please!\n";
		&DisplayUsage;
		}
if ($#ARGV<0) { print "\nI need a filename!\n";
		&DisplayUsage;
		}

# Set up a string var for printing out a quoted filename 
$fname="\"".$ARGV[0]."\"";

#### ---------------------------------------------------- ####
#### Read the data from the file named on the commandline ####
#### ---------------------------------------------------- ####
while (<ARGV>) { 
	chop;   
	# Pull the desired columns and save in data array
	push @data, substr($_,$startcol-1,$endcol-$startcol+1); 
	} # End of data input while loop

#### ---------------------------------------------------- ####
#### The real work begins here                            ####
#### ---------------------------------------------------- ####
# Get Frequencies 
foreach $value (@data) {
	$freq{$value}++;
	}
# Print Out the Frequencies
foreach $value (sort keys(%freq)) {
	$cfreq+=$freq{$value}; # compute cumulative freqs
	write; # this will be formatted by the formats at the end
	}
print "\n";

# Formatted, paged output
format STDOUT_TOP =
 
   @||||@||
   "Page",$%
   @<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<@<<<<<<<<<<<<
   "Frequencies for the values in columns",$loc
   @<<<<<<<<<<<@<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
   "in the file ",$fname
 
                                            Cumulative
                         Value   Frequency   Frequency
                        -------  ---------  ----------
.
format STDOUT =
   @>>>>>>>>>>>>>>>>>>>>>>>>>>>@>>>>>>>>>>@>>>>>>>>>>>
                     $value,   $freq{$value}, $cfreq 
.

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Last Modified: Sat Sep 6 20:43:38 EDT 2025