I want to validate phone number with following conditions:
length should be 10 digits
should start with 7 or 8 or 9
If it does not meet these requirements, we should fail the number.
I have tried the following:
print "Enter phone number: \n";
$name=<>;
chomp $name;
if (length($name)==10 && $name==~ m{/[^7-9]/}){
print "$name is valid \n";
}
else {
print "$name is not valid \n";
}
It might be worth explaining what was wrong with your original version. You have two checks. The first one (length($name)==10) is fine. The problems are with the second one.
$name==~ m{/[^7-9]/}
There are three problems here. Firstly, you're using the wrong operator. You know you need to bind your variable ($name) to your match operator, but the binding operator is =~ not ==~. But, unfortunately, your operator isn't wrong enough to throw a syntax error. Perl will interpret it as a numeric comparison (==) followed by a bitwise negation (~). That's certainly not what you want!
Your second problem is with the match operator. It looks like you know that the match operator is m/.../ and that you also know you can choose an alternative delimiter for the match operator - you've picked m{...}. But you shouldn't nest those delimiters. When you use m{/.../} you're are looking for two literal characters / in your string.
Finally, there's a problem with your actual regex. You want the string to start with 7, 8 or 9. Putting those digits in a character class ([7-9]) is a good idea. But you shouldn't also place the start of string anchor (^) inside the character class. At the start of a character class, ^ has a different meaning - it means "not one of the characters listed here". So your character class ends up meaning the exact opposite of what you wanted it to mean.
Your match expression should have looked like this:
$name =~ m{^[7-9]}
Making your complete code:
print "Enter phone number: \n";
$name = <>;
chomp $name;
if (length($name) == 10 and $name =~ m{^[7-9]}) {
print "$name is valid \n";
}
else {
print "$name is not valid \n";
}
(I did a little tidying - adding some whitespace around operators and switching && for and as is has lower precedence. You might also consider revising your variable name. $name is not a great name for a variable that contains a phone number!)
I would just use a single regex here:
^[789][0-9]{9}$
This avoids having to spread your validation logic across a few places.
if ($name =~ m{/^[789][0-9]{9}$/}){
print "$name is valid \n";
}
else {
print "$name is not valid \n";
}
Related
To achieve below task I have written below C like perl program (As I am new to Perl), But I am not sure if this is the best way to achieve.
Can someone please guide?
Note: Not with the full program, But where I can make improvement.
Thanks in advance
Input :
$str = "mail1, local<mail1#mail.local>, mail2#mail.local, <mail3#mail.local>, mail4 local<mail4#mail.local>"
Expected Output :
mail1, local<mail1#mail.local>
mail2#mail.local
<mail3#mail.local>
mail4, local<mail4#mail.local>
Sample Program
my $str="mail1, \#local<mail1\#mail.local>, mail2\#mail.local, <mail3\#mail.local>, mail4, local<mail4\#mail.local>";
my $count=0, #array, $flag=0, $tempStr="";
for my $c (split (//,$str)) {
if( ($count eq 0) and ($c eq ' ') ) {
next;
}
if($c) {
if( ($c eq ',') and ($flag eq 1) ) {
push #array, $tempStr;
$count=0;
$flag1=0;
$tempStr="";
next;
}
if( ($c eq '>' ) or ( $c eq '#' ) ) {
$flag=1;
}
$tempStr="$tempStr$c";
$count++;
}
}
if($count>0) {
push #array, $tempStr;
}
foreach my $var (#array) {
print "$var\n";
}
Edit:
Input:
Input is the output of above code.
Expected Output :
"mail1, local"<mail1#mail.local>
"mail4, local"<mail4#mail.local>
Sample Code:
$str =~ s/([^#>]+[#>][^,]+),\s*/$1\n/g;
my #addresses = split('\n',$str);
if(scalar #addresses) {
foreach my $address (#addresses) {
if (($address =~ /</) and ($address !~ /\"/) and ($address !~ /^</)){
$address="\"$address";
$address=~ s/</\"</g;
}
}
$str = join(',',#addresses);
}
print "$str\n";
As I see, you want to replace each:
comma and following spaces,
occurring after either # or >,
with a newline.
To make such replacement, instead of writing a parsing program, you can use
a regex.
The search part can be as follows:
([^#>]+[#>][^,]+),\s*
Details:
( - Start of the 1st capturing group.
[^#>]+ - A non-empty sequence of chars other than # or >.
[#>] - Either # or >.
[^,]+ - A non-empty sequence of chars other than a comma.
) - End of the 1st capturing group.
,\s* - A comma and optional sequence of spaces.
The replace part should be:
$1 - The 1st capturing group.
\n - A newline.
So the whole program, much shorter than yours, can be as follows:
my $str='mail1, local<mail1#mail.local>, mail2#mail.local, <mail3#mail.local>, mail4, local<mail4#mail.local>';
print "Before:\n$str\n";
$str =~ s/([^#>]+[#>][^,]+),\s*/$1\n/g;
print "After:\n$str\n";
To replace all needed commas I used g option.
Note that I put the source string in single quotes, otherwise Perl
would have complained about Possible unintended interpolation of #mail.
Edit
Your modified requirements must be handled different way.
"Ordinary" replacement is not an option, because now there are some
fragments to match and some framents to ignore.
So the basic idea is to write a while loop with a matching regex:
(\w+),?\s+(\w+)(<[^>]+>), meaning:
(\w+) - First capturing group - a sequence of word chars (e.g. mail1).
,?\s+ - Optional comma and a sequence of spaces.
(\w+) - Second capturing group - a sequence of word chars (e.g. local).
(<[^>]+>) - Third capturing group - a sequence of chars other than >
(actual mail address), enclosed in angle brackets, e.g. <mail1#mail.local>.
Within each execution of the loop you have access to the groups
captured in this particular match ($1, $2, ...).
So the content of this loop is to print all these captured groups,
with required additional chars.
The code (again much shorter than yours) should look like below:
my $str = 'mail1, local<mail1#mail.local>, mail2#mail.local, <mail3#mail.local>, mail4 local<mail4#mail.local>';
while ($str =~ /(\w+),?\s+(\w+)(<[^>]+>)/g) {
print "\"$1, $2\"$3\n";
}
Here is an approach using split, which in this case also needs a careful regex
use warnings;
use strict;
use feature 'say';
my $string = # broken into two parts for readabililty
q(mail1, local<mail1#mail.local>, mail2#mail.local, )
. q(<mail3#mail.local>, mail4, local<mail4#mail.local>);
my #addresses = split /#.+?\K,\s*/, $string;
say for #addresses;
The split takes a full regex in its delimiter specification. In this case I figure that each record is delimited by a comma which comes after the email address, so #.+?,
To match a pattern only when it is preceded by another brings to mind a negative lookbehind before the comma. But those can't be of variable length, which is precisely the case here.
We can instead normally match the pattern #.+? and then use the \K form (of the lookbehind) which drops all previous matches so that they are not taken out of the string. Thus the above splits on ,\s* when that is preceded by the email address, #... (what isn't consumed).
It prints
mail1, local<mail1#mail.local>
mail2#mail.local
<mail3#mail.local>
mail4, local<mail4#mail.local>
The edit asks about quoting the description preceding <...> when it's there. A simple way is to make another pass once addresses have been parsed out of the string as above. For example
my #addresses = split /#.+?\K,\s*/, $string; #/ stop syntax highlight
s/(.+?,\s*.+?)</"$1"</ for #addresses;
say for #addresses;
The regex in a loop is one way to change elements of an array. I use it for its efficiency (changes elements in place), conciseness, and as a demonstration of the following properties.
In a foreach loop the index variable (or $_) is an alias for the currently processed element – so changing it changes that element. This is a known source of bugs when allowed unknowingly, which was another reason to show it in the above form.
The statement also uses the statement modifier and it is equivalent to
foreach my $elem (#addresses) {
$elem =~ s/(.+?,\s*.+?)</"$1"</;
}
This is often considered a more proper way to write it but I find that the other form emphasizes more clearly that elements are being changed, when that is the sole purpose of the foreach.
Guys how do i check an empty input in perl? Including spaces,tabs,newlines etc..
here's my sample code but its not working: what am i doing wrong?
my $number=int (1+rand 100);
while (<>) {
chomp $_;
last if ($_=~/exit|quit/i or $_ eq $number);
print "too high! \n" if (defined $_ && $_ > $number);
print "too low!\n" if (defined $_ && $_ < $number);
print $_;
}
So basically, the user input something, if it's a number it compares to the default random number. It prints low or high depending on the number. But when i just press enter without entering something it still goes to that if statement and gives an error that what i entered isnt numeric (due to this code $_ < $number).
So another question is how to handle input to allow only the word "exit" or "quit" and numbers. Other than that it exits.
The while(<>){...} will loop as long as the return value of the <> is defined, i.e. you aren't at EOF. So $_ is always defined inside the loop.
To assert that some input is numeric, you can use looks_like_number from Scalar::Util or use a simple regex:
unless (/\A[0-9]+\z/) {
print "not numeric!\n";
next;
}
After that, we can treat the value of $_ as a number integer, and can be sure that use warnings won't complain. E.g.
# remove newline from input
chomp;
# Test for abort condition
last if /\b(?:quit|exit)\b/;
# Assert numeric input
unless (/\A[0-9]+\z/) {
print "not numeric!\n";
next;
}
# Check input against secret $number
if ($_ == $number) {
print "Correct!\n";
last;
} elsif ($_ < $number) {
print "too low\n";
} elsif ($_ > $number) {
print "too high\n";
}
Sorry for the silly question, Got the answer to my first question.
you just have to add this code to the first condition
$_=~/^\s*$/
which compares if the input is any whitespace
and for the second one to limit only the "exit" and "quit" as a valid non digit input add this one to the first regex comparison in the first condition
$_=~/(exit|quit|\D)/i
notice the \D which only matches non digit characters. But since its an "OR" it will short circuit once a specific non digit character (exit or quit) is entered, terminating the loop instantly.
Thanks guys
I am having quite a bit of trouble with a Perl script I am writing. I want to compare an element of an array to a variable I have to see if they are true. For some reason I cannot seem to get the comparison operation to work correctly. It will either evaluate at true all the time (even when outputting both strings clearly shows they are not the same), or it will always be false and never evaluate (even if they are the same). I have found an example of just this kind of comparison operation on another website, but when I use it it doesn't work. Am I missing something? Is the variable type I take from the file not a string? (Can't be an integer as far as I can tell as it is an IP address).
$ipaddress = '192.43.2.130'
if ($address[0] == ' ')
{
open (FH, "serverips.txt") or die "Crossroads could not find a list of backend servers";
#address = <FH>;
close(FH);
print $address[0];
print $address[1];
}
for ($i = 0; $i < #address; $i++)
{
print "hello";
if ($address[$i] eq $ipaddress)
{print $address[$i];
$file = "server_$i";
print "I got here first";
goto SENDING;}
}
SENDING:
print " I am here";
I am pretty weak in Perl, so forgive me for any rookie mistakes/assumptions I may have made in my very meager bit of code. Thank you for you time.
if ($address[0] == ' ')
{
open (FH, "serverips.txt") or die "Crossroads could not find a list of backend servers";
#address = <FH>;
close(FH);
You have several issues with this code here. First you should use strict because it would tell you that #address is being used before it's defined and you're also using numeric comparison on a string.
Secondly you aren't creating an array of the address in the file. You need to loop through the lines of the file to add each address:
my #address = ();
while( my $addr = <FH> ) {
chomp($addr); # removes the newline character
push(#address, $addr);
}
However you really don't need to push into an array at all. Just loop through the file and find the IP. Also don't use goto. That's what last is for.
while( my $addr = <FH> ) {
chomp($addr);
if( $addr eq $ipaddress ) {
$file = "server_$i";
print $addr,"\n";
print "I got here first"; # not sure what this means
last; # breaks out of the loop
}
}
When you're reading in from a file like that, you should use chomp() when doing a comparison with that line. When you do:
print $address[0];
print $address[1];
The output is on two separate lines, even though you haven't explicitly printed a newline. That's because $address[$i] contains a newline at the end. chomp removes this.
if ($address[$i] eq $ipaddress)
could read
my $currentIP = $address[$i];
chomp($currentIP);
if ($currentIP eq $ipaddress)
Once you're familiar with chomp, you could even use:
chomp(my $currentIP = $address[$i]);
if ($currentIP eq $ipaddress)
Also, please replace the goto with a last statement. That's perl's equivalent of C's break.
Also, from your comment on Jack's answer:
Here's some code you can use for finding how long it's been since a file was modified:
my $secondsSinceUpdate = time() - stat('filename.txt')->mtime;
You probably are having an issue with newlines. Try using chomp($address[$i]).
First of all, please don't use goto. Every time you use goto, the baby Jesus cries while killing a kitten.
Secondly, your code is a bit confusing in that you seem to be populating #address after starting the if($address[0] == '') statement (not to mention that that if should be if($address[0] eq '')).
If you're trying to compare each element of #address with $ipaddress for equality, you can do something like the following
Note: This code assumes that you've populated #address.
my $num_matches=0;
foreach(#address)
{
$num_matches++ if $_ eq $ipaddress;
}
if($num_matches)
{
#You've got a match! Do something.
}
else
{
#You don't have any matches. This may or may not be bad. Do something else.
}
Alternatively, you can use the grep operator to get any and all matches from #address:
my #matches=grep{$_ eq $ipaddress}#address;
if(#matches)
{
#You've got matches.
}
else
{
#Sorry, no matches.
}
Finally, if you're using a version of Perl that is 5.10 or higher, you can use the smart match operator (ie ~~):
if($ipaddress~~#address)
{
#You've got a match!
}
else
{
#Nope, no matches.
}
When you read from a file like that you include the end-of-line character (generally \n) in each element. Use chomp #address; to get rid of it.
Also, use last; to exit the loop; goto is practically never needed.
Here's a rather idiomatic rewrite of your code. I'm excluding some of your logic that you might need, but isn't clear why:
$ipaddress = '192.43.2.130'
open (FH, "serverips.txt") or die "Crossroads could not find a list of backend servers";
while (<FH>) { # loop over the file, using the default input space
chomp; # remove end-of-line
last if ($_ eq $ipaddress); # a RE could easily be used here also, but keep the exact match
}
close(FH);
$file = "server_$."; # $. is the line number - it's not necessary to keep track yourself
print "The file is $file\n";
Some people dislike using perl's implicit variables (like $_ and $.) but they're not that hard to keep track of. perldoc perlvar lists all these variables and explains their usage.
Regarding the exact match vs. "RE" (regular expression, or regexp - see perldoc perlre for lots of gory details) -- the syntax for testing a RE against the default input space ($_) is very simple. Instead of
last if ($_ eq $ipaddress);
you could use
last if (/$ipaddress/);
Although treating an ip address as a regular expression (where . has a special meaning) is probably not a good idea.
Why will my script not work correctly?
I follow a YouTube video and worked for the guy.
I am running Perl on Windows using ActiveState ActivePerl 5.12.2.1202
Here is my tiny tiny code block.
print "What is your name?\n";
$name = <STDIN>;
if ($name eq "Jon") {
print "We have met before!\n";
} else {
print "We have not met before.\n";
}
The code automatically jumps to the else statement and does not even check the if statement.
The statement $name = <STDIN>; reads from standard input and includes the terminating newline character "\n". Remove this character using the chomp function:
print "What is your name?\n";
$name = <STDIN>;
chomp($name);
if ($name eq "Jon") {
print "We have met before!\n";
} else {
print "We have not met before.\n";
}
The trick in programming is to know what your data are. When something's not acting like you expect, look at the data to see if they are what you expect. For instance:
print "The name is [$name]\n";
You put the braces around it so you can see any extra whitespace that might be there. In this case, you would have seen:
The name is [Jon
]
That's your clue that there is extra stuff. Since the eq has to match exactly, it fails to match.
If you're just starting with Perl, try Learning Perl. It's much better than random videos from YouTube. :)
When you read the name standard input as $name = <STDIN>;
$name will have a trailing newline. So if I enter foo , $name will actually have foo\n.
To get rid of this newline you an make use of the chomp function as:
chomp($name = <STDIN>);
$value = $list[1] ~ s/\D//g;
syntax error at try1.pl line 53, near "] ~"
Execution of try1.pl aborted due to compilation errors.
I am trying to extract the digits from the second element of #list, and store it into $value.
You mean =~, not ~. ~ is a unary bitwise negation operator.
A couple of ways to do this:
($value) = $list[1] =~ /(\d+)/;
Both sets of parens are important; only if there are capturing parentheses does the match operation return actual content instead of just an indication of success, and then only in list context (provided by the list-assign operator ()=).
Or the common idiom of copy and then modify:
($value = $list[1]) =~ s/\D//;
maybe you wanted the =~ operator?
P.S. note that $value will not get assigned the resulting string (the string itself is changed in place). $value will get assigned the number of substitutions that were made
You said in a comment that are trying to get rid of non-digits. It looks like you are trying to preserve the old value and get the modified value in a new variable. The Perl idiom for that is:
( my $new = $old ) =~ s/\D//g;
And wanted \digits not non-\Digits. And have a superfluous s/ubstitute operator where a match makes more sense.
if ($list[1] =~ /(\d+)/) {
$value = $1;
}