I use an ActivePerl script to take in CSV files and create XML files that I load into a database. These are userid database entries, name, address, etc. We've always used the home phone number field to generate an initial password (which we encourage the users to change immediately!). The proliferation of cellphones means I have a bunch of people with no home phone, so I want to use the cell phone field when the home phone field is empty.
My input fields look like this:
# 0 Firstname
# 1 Lastname
# 2 VP (voicepart)
# 3 Address
# 4 City
# 5 State
# 6 Zip
# 7 Phone
# 8 Mobile
# 9 Email
Here's the Perl code I've worked up to create the password - the create_password subroutine is working when there's a value in field 7:
my $pass_word = '';
my $pass_word = create_password($fields[7]);
if (my $pass_word = '') {
print "Use the cell phone number \n";
my $pass_word = create_password($fields[8]);
}
The "print" statement is to tell me what it thinks it's doing.
This looks to me like it should work, but the "if" statment never fires. The Print statement doesn't print, and nobody with a value only in field 8 ever gets a password generated. There must be something wrong with the way I'm testing the value of $pass_word but I can't see it. Should I be testing the values of $fields[7] and $fields[8] instead of the variable value? How DO you test a Perl variable for null value if this doesn't work?
You have several problems in your code.
First of all, after you declared a variable using my, you don't need to add my before the variable when you use it;
Secondly, for this line:
if (my $pass_word = '')
I think you meant
if ($pass_word == '')
(my is removed, as talked in the first point)
= means assignment, which returns the value you assigned to $pass_word, which is '' here, that's why this condition always return false.
But still, == is not correct here. In perl, we use eq to compare two strings. == is used to compare numbers.
So, remove all the my except the first one, and use eq to compare your strings.
You've got two major problems in here.
First one is your string equality test. In Perl, strings are compared for equality using operator eq (as in $string eq 'something'). = is the assignment operator.
Second one is your (ab)use of my. Each my declares a new variable that “hides” the previous one, so in effect you can never re-use its value, you're confronted to undef every time.
Replace = with eq in your if clause; remove all but the first uses of my, and you should be set!
my declares a new variable which hides the variable with the same name in the surrounding scope. Remove the excessive use of my.
Related
I have a two-column data set in a tab-separated .txt file, and the perl script reads it as FH and this is the immediate snippet of code that follows:
while(<FH>)
{
chomp;
s/\r//;
/(.+)\t(.+)/;
$uniq_tar{$2}++;
$uniq_mir{$1}++;
push#{$mir_arr{$1}},$2;
push #{$target{$2}} ,$1;
}
When I try to print any of the above 4 variables, it says the variables are uninitialized.
And, when I tried to print $uniq_tar{$2}++; and $uniq_mir{$1}++;
It just prints some numbers which I cannot understand.
I would just like to know what this part of code evaluate in general?
$uniq_tar{$2}++;
The while loop puts each line of your file, in turn, into Perl's special variable $_.
/.../ is the match operator. By default it works on $_.
/(.*)\t(.*)/ is a regular expression inside the match operator. If the regex matches what is in $_, then the bits of the matching string that are inside the two pairs of parentheses are stored in Perl's special variables $1 and $2.
You have hashes called %uniq_tar and %uniq_mir. You access individual elements in a hash using the $hashname{key}. So, $uniq_tar{$1} is finding the value in %uniq_tar associated with the key that is stored in $1 (that is - the part of your record before the first tab).
$variable++ increments the number in $variable. So $uniq_tar{$1}++ increments the value that we found in the previous paragraph.
So, as zdim says, it's a frequency counter. You read each line in the file, and extract the bits of data before and after the first tab in the line. You then increment the values in two hashes to count the number of occurences of each of the strings.
I am still learning perl and have all most got a program written. My question, as simple as it may be, is if I want to hardcode a string to a field would the below do that? Thank you :).
$out[45]="VUS";
In the other lines I use the below to define the values that are passed into the `$[out], but the one in question is hardcoded and the others come from a split.
my #vals = split/\t/; # this splits the line at tabs
my #mutations=split/,/,$vals[9]; # splits on comma to create an array of mutations
my ($gene,$transcript,$exon,$coding,$aa);
for (#mutations)
{
($gene,$transcript,$exon,$coding,$aa) = split/\:/; # this takes col AB and splits it at colons
grep {$transcript eq $_} keys %nms or next;
}
my #out=($.,#colsleft,$_,#colsright);
$out[2]=$gene;
$out[3]=$nms{$transcript};
$out[4]=$transcript;
$out[15]=$coding;
$out[17]=$aa;
Your line of code: $out[45]="VUS"; is correct in that it is defining that 46th element of the array #out to the string, "VUS". I am trying to understand from your code, however why you would want to do that? Usually, it is better practice to not hardcode if at all possible. You want to make it your goal to make your program as dynamic as possible.
I am trying to extract a part of a string and put it into a new variable. The string I am looking at is:
maker-scaffold_26653|ref0016423-snap-gene-0.1
(inside a $gene_name variable)
and the thing I want to match is:
scaffold_26653|ref0016423
I'm using the following piece of code:
my $gene_name;
my $scaffold_name;
if ($gene_name =~ m/scaffold_[0-9]+\|ref[0-9]+/) {
$scaffold_name = $1;
print "$scaffold_name\n";
}
I'm getting the following error when trying to execute:
Use of uninitialized value $scaffold_name in concatenation (.) or string
I know that the pattern is right, because if I use $' instead of $1 I get
-snap-gene-0.1
I'm at a bit of a loss: why will $1 not work here?
If you want to use a value from the matching you have to make () arround the character in regex
To expand on Jens' answer, () in a regex signifies an anonymous capture group. The content matched in a capture group is stored in $1-9+ from left to right, so for example,
/(..):(..):(..)/
on an HH:MM:SS time string will store hours, minutes, and seconds in $1, $2, $3 respectively. Naturally this begins to become unwieldy and is not self-documenting, so you can assign the results to a list instead:
my ($hours, $mins, $secs) = $time =~ m/(..):(..):(..)/;
So your example could bypass the use of $ variables by doing direct assignment:
my ($scaffold_name) = $gene_name =~ m/(scaffold_[0-9]+[|]ref[0-9]+)/;
# $scaffold_name now contains 'scaffold_26653|ref0016423'
You can even get rid of the ugly =~ binding by using for as a topicalizer:
my $scaffold_name;
for ($gene_name) {
($scaffold_name) = m/(scaffold_\d+[|]ref\d+)/;
print $scaffold_name;
}
If things start to get more complex, I prefer to use named capture groups (introduced in Perl v5.10.0):
$gene_name =~ m{
(?<scaffold_name> # ?<name> creates a named capture group
scaffold_\d+? # 'scaffold' and its trailing digits
[|] # Literal pipe symbol
ref\d+ # 'ref' and its trailing digits
)
}xms; # The x flag lets us write more readable regexes
print $+{scaffold_name}, "\n";
The results of named capture groups are stored in the magic hash %+. Access is done just like any other hash lookup, with the capture groups as the keys. %+ is locally scoped in the same way the $ are, so it can be used as a drop-in replacement for them in most situations.
It's overkill for this particular example, but as regexes start to get larger and more complicated, this saves you the trouble of either having to scroll all the way back up and count anonymous capture groups from left to right to find which of those darn $ variables is holding the capture you wanted, or scan across a long list assignment to find where to add a new variable to hold a capture that got inserted in the middle.
My personal rule of thumb is to assign the results of anonymous captured to descriptively named lexically scoped variables for 3 or less captures, then switch to using named captures, comments, and indentation in regexes when more are necessary.
In if condition I used to take one value from log file after matching the particular pattern. That pattern is matched two times in log file. While matching the pattern first time that value is 0 and second time value is 48. It may be also reverse. First value may contain 48 and second value may contain 0. I need to calculate the exact value. So I planned to add these two values. but after adding these two values also while printing the total value in if condition I used to get the two values separately. But I need single value only.
Please give me solution to solve this issue.
Thanks in advance.
Do you mean something like this:
my $entry = "First is 10, seconds is 48";
if(my ($a,$b) = $entry =~ /(\d+)/g) {
print $a + $b,"\n"; # 58
}
But without actual code it is hard to see what your problem really is.
I have these three lines in bash that work really nicely. I want to add them to some existing perl script but I have never used perl before ....
could somebody rewrite them for me? I tried to use them as they are and it didn't work
note that $SSH_CLIENT is a run-time parameter you get if you type set in bash (linux)
users[210]=radek #where 210 is tha last octet from my mac's IP
octet=($SSH_CLIENT) # split the value on spaces
somevariable=$users[${octet[0]##*.}] # extract the last octet from the ip address
These might work for you. I noted my assumptions with each line.
my %users = ( 210 => 'radek' );
I assume that you wanted a sparse array. Hashes are the standard implementation of sparse arrays in Perl.
my #octet = split ' ', $ENV{SSH_CLIENT}; # split the value on spaces
I assume that you still wanted to use the environment variable SSH_CLIENT
my ( $some_var ) = $octet[0] =~ /\.(\d+)$/;
You want the last set of digits from the '.' to the end.
The parens around the variable put the assignment into list context.
In list context, a match creates a list of all the "captured" sequences.
Assigning to a scalar in a list context, means that only the number of scalars in the expression are assigned from the list.
As for your question in the comments, you can get the variable out of the hash, by:
$db = $users{ $some_var };
# OR--this one's kind of clunky...
$db = $users{ [ $octet[0] =~ /\.(\d+)$/ ]->[0] };
Say you have already gotten your IP in a string,
$macip = "10.10.10.123";
#s = split /\./ , $macip;
print $s[-1]; #get last octet
If you don't know Perl and you are required to use it for work, you will have to learn it. Surely you are not going to come to SO and ask every time you need it in Perl right?