I am working on a user login and am having trouble with the user creation part. My problem is that I am trying to check the input username against a text file to see if that username already exists. I can't seem to get it to compare the input username to the array that I have brought in. I have tried two different ways of accomplishing this. One using an array and another using something I read online that I don't quite understand. Any help or explanation would be greatly appreciated.
Here is my attempt using an array to compare off of
http://codepad.org/G7xmsf3z
Here is my second attempt
http://codepad.org/SbeqmdbG
In your first attempt, try to put the if inside of the loop:
foreach my $pair(#incomingarray) {
(my $name,my $value) = split (/:/, $pair);
if ($name eq $username) {
print p("Username is already taken, try again");
close(YYY);
print end_html();
}
else {
open(YYY, ">>password.txt");
print YYY $username.":".$hashpass."\n";
print p("Your account has been created sucessfully");
close(YYY);
print end_html();
}
}
In you second attempt, I think you should try and change the line:
if (%users eq $username) {
with this one:
if (defined $users{$username}) {
As has been stated above regarding locking the flatfile from other processes there is the issue with scaling too. the more users you have the slower the lookup will be.
I started years ago with a flat file, believing I would never scale enough to require a real database and didn't want to learn how to use mySQL for example. Eventually after flatfile corruptions and long lookup times I had no choice but to move to a database.
Later you will find yourself wanting to store user preferences and such, it's easy to add a new field to a database. Flatfile will end up having the overhead of splitting each line into separate fields.
I'd suggest you do it properly with a database.
As in my comment, you should not be using a flatfile to hold your user info. You should use a proper database that will handle concurrent access for you rather than having to understand and code up how to deal with all of that yourself!
If you insist on using an array, you can search it with grep() if it is not "too large":
if (grep /^$username:/, #incomingarray) {
print "user name '$username' is already registered, try again\n";
}
else {
print "user name '$username' is not already registered\n";
}
I see some other problems in your code as well.
You should always prefer lexical (my) variables over package (our) variables.
Why do you think (erroneously) that $name and $username cannot be lexical variables?
You should always use the 3-arg form of open() and check its return value like in your 2nd code example. Your open() in the 1st code example is how it was done many many years ago.
Related
I'm writing a perl script to retrieve search results from a Xapian database.
I uses the Search::Xapian module and tried the basic Xapian Query Example. This basic program allow to make a query and get a array of results sorted by relevancy. My problem is that the get_data() method return the whole datas from the document (url, filname, abstract, author, ...) mixed together as a string.
I searched in the CPAN module for a method to get each data one by one but I didn't find it.
Is it possible to get the filename, url, author, ... one by one to put them in a specific variable ?
You've not posted the code to produce this, or details of your setup. See the simplesearch.pl example, rather than print it out, assign what you want to a variable:
# Display the results.
printf "%i results found.\n", $mset->get_matches_estimated();
printf "Results 1-%i:\n", $mset->size();
foreach my $m ($mset->items()) {
printf "%i: %i%% docid=%i [%s]\n", $m->get_rank() + 1, $m->get_percent(), $m->get_docid(), $m->get_document()->get_data();
}
everyone.
I'm doing an tool with Perl that actually verifies a status in the database and if necessary it gets the properly queries and after confirmation it updates the value.
The page has three possible contents:
If the query that will be used is already filled it updates and returns the status.
If only the serial that the user input is filled it generates the query and then asks for confirmation.
If none of those 2 variables are already filled it goes to the main form where the user can submit the serial.
The problem that I'm facing is that after it generates the $final_query and shows up for confirmation, when I click the Confirm button it reloads the page but it pass directly through the if($final_query) and even the elseif that verifies if the $serial_no is already set.
Does Perl really lose those values if I perform a second submit or am I doing something wrong?
I'd love to have some explanation about it because it's the second time that I'm doing something with that language.
Thanks in advance!
--edit
I chopped the code to show where it defines the $final_query but I kept the structure to help in the understanding.
The full code is available at http://pastebin.com/6NqhbVau
#headers
if ($final_query) {
$content = "<h1>first if</h1>";
#updateESNDatabase($database, $final_query);
#it only enters here if the user type the ESN
}elsif ($serial_no) {
#selects the database
switch(checkUpdateNeeded($database, $serial_no)) {
case 0 {
#Shows that the updates are no needed
}
case 1 {
$final_query = `cat $query1`;
chop($final_query);
$final_query =~ s/SERIALNUM/$serial_no/g;
$final_query =~ s/LOGINID/$login_id/g;
$content = $cgi->start_form .
"<center>" .
"<h3> Please double check the queries below before you update on database </h3>" .
"</center>" .
$cgi->submit("Confirm") . $cgi->end_form;
$content .= $final_query;
}
case 2 {
#Makes almost the same as the first case, it only uses a different file to generate the query.
}
}
} else {
#Generates the first page, where the users inputs information
}
$page->set_content($content);
$page->process;
I figured out how to perform this.
As per my analysis I cannot simply create a variable and pass it through the cgi form.
To workaround this what I've done is create a hidden input in HTML and then send the variable through it.
<input type='hidden' name='the_query' value=\"$final_query\">
I'm using HOP::Lexer to scan BlitzMax module source code to fetch some data from it. One particular piece of data I'm currently interested in is a module description.
Currently I'm searching for a description in the format of ModuleInfo "Description: foobar" or ModuleInfo "Desc: foobar". This works fine. But sadly, most modules I scan have their description defined elsewhere, inside a comment block. Which is actually the common way to do it in BlitzMax, as the documentation generator expects it.
This is how all modules have their description defined in the main source file.
Rem
bbdoc: my module description
End Rem
Module namespace.modulename
This also isn't really a problem. But the line after the End Rem also contains data I want (the module name). This is a problem, since now 2 definitions of tokens overlap each other and after the first one has been detected it will continue from where it left off (position of content that's being scanned). Meaning that the token for the module name won't detect anything.
Yes, I've made sure my order of tokens is correct. It just doesn't seem possible (somewhat understandable) to move the cursor back a line.
A small piece of code for fetching the description from within a Rem-End Rem block which is above a module definition (not worked out, but working for the current test case):
[ 'MODULEDESCRIPTION',
qr/[ \t]*\bRem\n(?:\n|.)*?\s*\bEnd[ \t]*Rem\nModule[\s\t]+/i,
sub {
my ($label, $value) = #_;
$value =~ /bbdoc: (.+)/;
[$label, $1];
}
],
So in my test case I first scan for a single comment, then the block above (MODULEDESCRIPTION), then a block comment (Rem-End Rem), module name, etc.
Currently the only solution I can think of is setup a second lexer only for the module description, though I wouldn't prefer that. Is what I want even possible at all with HOP::Lexer?
Source of my Lexer can be found at https://github.com/maximos/maximus-web/blob/develop/lib/Maximus/Class/Lexer.pm
I've solved it by adding (a slightly modified version of) the MODULEDESCRIPTION. Inside the subroutine I simply filter out the module name and return an arrayref with 4 elements, which I later on iterate over to create a nice usable array with tokens and their values.
Solution is again at https://github.com/maximos/maximus-web/blob/develop/lib/Maximus/Class/Lexer.pm
Edit: Or let me just paste the piece of code here
[ 'MODULEDESCRIPTION',
qr/[ \t]*\bRem\R(?:\R|.)*?\bEnd[ \t]*Rem\R\bModule[\s\t]\w+\.\w+/i,
sub {
my ($label, $value) = #_;
my ($desc) = ($value =~ /\bbbdoc: (.+)/i);
my ($name) = ($value =~ /\bModule (\w+\.\w+)/i);
[$label, $desc, 'MODULENAME', $name];
}
],
I am trying to extract data from website using perl API. The process is to use a list of uris as input. Then I extract related information for each uri from website. If the information for one uri is not present it dies. Some thing like the code below
my #tags = $c->posts_for(uri =>"$currentURI");
die "No candidate related articles\n" unless #tags;
Now, I don't want the program to stop if it doesn't get any tags. I want the program to skip that particular uri and go to the next available uri. How can i do it?
Thank you for your time and help.
Thank you,
Sammed
Well, assuming that you're inside a loop processing each of the URIs in turn, you should be able to do something like:
next unless #tags;
For example, the following program only prints lines that are numeric:
while (<STDIN>) {
next unless /^\d+$/;
print;
}
The loop processes every input line in turn but, when one is found that doesn't match that regular expression (all numeric), it restarts the loop (for the next input line) without printing.
The same method is used in that first code block above to restart the loop if there are no tags, moving to the next URI.
Besides the traditional flow control tools, i.e. next/last in a loop or return in a sub, one can use exceptions in perl:
eval {
die "Bad bad thing";
};
if ($#) {
# do something about it
};
Or just use Try::Tiny.
However, from the description of the task it seems next is enough (so I voted for #paxdiablo's answer).
The question is rather strange, but as near as I can tell, you are asking how to control the flow of your current loop. Of course, using die will cause your program to exit, so if you do not want that, you should not use die. Seems elementary to me, that's why it is a strange questions.
So, I assume you have a loop such as:
for my $currentURI (#uris) {
my #tags = $c->posts_for(uri =>"$currentURI");
die "No candidate related articles\n" unless #tags;
# do stuff with #tags here....
}
And if #tags is empty, you want to go to the next URI. Well, that's a simple thing to solve. There are many ways.
next unless #tags;
for my $tag (#tags) { ... stuff ... }
if (#tags) { .... }
Next is the simplest one. It skips to the end of the loop block and starts with the next iteration. However, using a for or if block causes the same behaviour, and so are equivalent. For example:
for my $currentURI (#uris) {
my #tags = $c->posts_for(uri =>"$currentURI");
for my $tag (#tags) {
do_something($tag);
}
}
Or even:
for my $currentURI (#uris) {
for my $tag ($c->posts_for(uri =>"$currentURI")) {
do_something($tag);
}
}
In this last example, we removed #tags all together, because it is not needed. The inner loop will run zero times if there are no "tags".
This is not really complex stuff, and if you feel unsure, I suggest you play around a little with loops and conditionals to learn how they work.
I'm in a web scripting class, and honestly and unfortunately, it has come second to my networking and design and analysis classes. Because of this I find I encounter problems that may be mundane but can't find the solution to it easily.
I am writing a CGI form that is supposed to work with a MySQL DB. I can insert and delete into the DB just fine. My problem comes when querying the DB.
My code compiles fine and I don't get errors when trying to "display" the info in the DB through the browser but the data and text doesn't in fact display. The code in question is here:
print br, 'test';
my $dbh = DBI->connect("DBI:mysql:austinc4", "*******", "*******", {RaiseError => 1} );
my $usersstatement = "select * from users";
my $projstatment = "select * from projects";
# Get the handle
my $userinfo = $dbh->query($usersstatement);
my $projinfo = $dbh->query($projstatement);
# Fetch rows
while (#userrow = $userinfo->fetchrow()) {
print $userrow[0], br;
}
print 'end';
This code is in an if statement that is surrounded by the print header, start_html, form, /form, end_html. I was just trying to debug and find out what was happening and printed the statements test and end. It prints out test but doesn't print out end. It also doesn't print out the data in my DB, which happens to come before I print out end.
What I believe I am doing is:
Connecting to my DB
Forming a string the contains the command/request to the DB
Getting a handle for my query I perform on the DB
Fetching a row from my handle
Printing the first field in the row I fetched from my table
But I don't see why my data wouldn't print out as well as the end text. I looked in DB and it does in fact contain data in the DB and the table that I am trying to get data from.
This one has got me stumped, so I appreciate any help. Thanks again. =)
Solution:
I was using a that wasn't supported by the modules I was including. This leads me to another question. How can I detect errors like this? My program does in fact compile correctly and the webpage doesn't "break". Aside from me double checking that all the methods I do use are valid, do I just see something like text not being displayed and assume that an error like this occurred?
Upon reading the comments, the reason your program is broken is because query() does not execute an SQL query. Therefore you are probably calling an undefined subroutine unless this is a wrapper you have defined elsewhere.
Here is my original posting of helpful hints, which still apply:
I hope you have use CGI, use DBI, etc... and use CGI::Carp and use strict;
Look in /var/log/apache2/access.log or error.log for the bugs
Realize that the first thing a CGI script prints MUST be a valid header or the web server and browser become unhappy and often nothing else displays.
Because of #3 print the header first BEFORE you do anything, especially before you connect to the database where the script may die or print something else because otherwise the errors or other messages will be emitted before the header.
If you still don't see an error go back to #2.
CGIs that use CGI.pm can be run from a command line in a terminal session without going through the webserver. This is also a good way to debug.