winsem2013-14_cp3057_28-jan-2014_rm01_demopattern1 (1)

8/12/2019 WINSEM2013-14_CP3057_28-Jan-2014_RM01_demopattern1 (1)

1/10

#!/usr/local/bin/perl

######## A word-count program that handles multiple spaces between words.

$wordcount = 0;

$line = ;

while ($line ne "") {

chop ($line);

@words = split(/ +/, $line);

$wordcount += @words;

$line = ;

}

print ("Total number of words: $wordcount\n");

#o/p

#$ program7_2

#Here is some input.

#Here are some more words.

#Here is my last line.

#^D

#Total number of words: 14

##############################################################################

#####


2/10

##############################################################################

#####

########A simple variable-name validation program.

print ("Enter a variable name:\n");

$varname = ;

chop ($varname);

if ($varname =~ /\$[A-Za-z][_0-9a-zA-Z]*/) {

print ("$varname is a legal scalar variable\n");

} elsif ($varname =~ /@[A-Za-z][_0-9a-zA-Z]*/) {

print ("$varname is a legal array variable\n");

} elsif ($varname =~ /[A-Za-z][_0-9a-zA-Z]*/) {

print ("$varname is a legal file variable\n");

} else {

print ("I don't understand what $varname is.\n");

}

#Enter a variable name:

#$result

#$result is a legal scalar variable

##############################################################################

#####


3/10

##############################################################################

#####

######## A program that counts the number of input lines containing the word the.

$thecount = 0;

print ("Enter the input here:\n");

$line = ;

while ($line ne "") {

if ($line =~ /\bthe\b/) {

$thecount += 1;

}

$line = ;

}

print ("Number of lines containing 'the': $thecount\n");

#Enter the input here:

#Now is the time

#for all good men

#to come to the aid

#of the party.

#^D

#Number of lines containing 'the': 3

##############################################################################

#####

######## A simple pattern-search program.

print ("Enter the search pattern:\n");


4/10

$pattern = ;

chop ($pattern);

$filename = $ARGV[0];

$linenum = $matchcount = 0;

print ("Matches found:\n");

while ($line = ) {

$linenum += 1;

if ($line =~ /$pattern/) {

print ("$filename, line $linenum\n");

@words = split(/$pattern/, $line);

$matchcount += @words - 1;

}

if (eof) {

$linenum = 0;

$filename = $ARGV[0];

}

}

if ($matchcount == 0) {

print ("No matches found.\n");

} else {

print ("Total number of matches: $matchcount\n");

}

#perl current_program.pl file1 file2

#Enter the search pattern:


5/10


6/10

$input[$count] =~ s/^[ \t]+//;

$input[$count] =~ s/[ \t]+\n$/\n/;

$input[$count] =~ s/[ \t]+/ /g;

$count++;

}

print ("Formatted text:\n");

print (@input);

#This is a line of input.

# Here is another line.

#This is my last line of input.

#^D

#Formatted text:

#This is a line of input.

#Here is another line.

#This is my last line of input.

##############################################################################

#####

######## ### Pattern Matching ###


7/10

## Find the word "Perl"

$pattern = 'Perl';

## Find "Perl" at the beginning of a line

$pattern = '^Perl';

## Find sentences that contain an "i"

$pattern = 'i';

## Find words starting in "i", i.e. a space preceeds the letter

$pattern = '\si';

## Find strings containing a digit

$pattern = '\d';

## Search for a digit followed by some stuff

$pattern = '\d+.+';

## Find strings with a digit at the end of a line

$pattern = '\d+$';

## Search for a digit, possible stuff in between, and another digit

$pattern = '\d.*\d';


8/10

## Find four-letter words, i.e. four characters offset by word boundaries

$pattern = '\b\w{4}\b';

## Sentences with three words, three word fields separated by white space

$pattern = '\w+\s+\w+\s+\w+';

## Find sentences with two "e" letters, and possible stuff between

$pattern = 'e.*e';

##############################################################################

#####

############ Marking Regular Expression Sub-strings and Using Substitution

## Find five-letter words and replace with "Amazing"

$pattern = '\b\w{5}\b';

foreach(@strings)

{s/$pattern/Amazing/;

}

## Search for two digits in same line, and switch their positions

foreach(@strings)

{ $pattern = '(\d)(.*)(\d)';


9/10

if (/$pattern/)

{ print "Grabbed pattern: $pattern \$1 = $1 \$2 = $2 \$3 = $3\n";

s/$pattern/$3$2$1/;

}

}

##############################################################################

#####

########

##############################################################################

#####

########

# change all occurances of a string in a file to another string

#

if ($#ARGV != 3) {

print "usage: chstring oldfile newfile oldstring newstring\n";

exit;

}

$oldfile = $ARGV[0];

$newfile = $ARGV[1];

$old = $ARGV[2];

$new = $ARGV[3];


10/10

open(OF, $oldfile);

open(NF, ">$newfile");

# read in each line of the file

while ($line = ) {

$line =~ s/$old/$new/;

print NF $line;

}

close(OF);

close(NF);

##############################################################################

#####

########

winsem2013-14_cp3057_28-jan-2014_rm01_demopattern1 (1)

Documents