This snippet basically reads a file line by line, which looks something like:
Album=In Between Dreams
Interpret=Jack Johnson
Titel=Better Together
Titel=Never Know
Titel=Banana Pancakes
Album=Pictures
Interpret=Katie Melua
Titel=Mary Pickford
Titel=It's All in My Head
Titel=If the Lights Go Out
Album=All the Lost Souls
Interpret=James Blunt
Titel=1973
Titel=One of the Brightest Stars
So it somehow connects the "Interpreter" with an album and this album with a list of titles. But what I don't quite get is how:
while ($line = <IN>) {
chomp $line;
if ($line =~ /=/) {
($name, $wert) = split(/=/, $line);
}
else {
next;
}
if ($name eq "Album") {
$album = $wert;
}
if ($name eq "Interpret") {
$interpret = $wert;
$cd{$interpret}{album} = $album; // assigns an album to an interpreter?
$titelnummer = 0;
}
if ($name eq "Titel") {
$cd{$interpret}{titel}[$titelnummer++] = $wert; // assigns titles to an interpreter - WTF? how can this work?
}
}
The while loop keeps running and putting the current line into $line as long as there are new lines in the file handle <IN>. chomp removes the newline at the end of every row.
split splits the line into two parts on the equal sign (/=/ is a regular expression) and puts the first part in $name and the second part in $wert.
%cd is a hash that contains references to other hashes. The first "level" is the name of interpreter.
(Please ask more specific questions if you still do not understand.)
cd is a hash of hashes.
$cd{$interpret}{album} contains album for interpreter.
$cd{$interpret}{titel} contains an array of Titel, which is filled incrementally in the last if.
Perl is a very concise language.
The best way to figure out what's going on is to inspect the data structure. After the while loop, temporarily insert this code:
use Data::Dumper;
print '%cd ', Dumper \%cd;
exit;
This may have a large output if the input is large.
Related
I have searched a fair bit and hope I'm not duplicating something someone has already asked. I have what amounts to a CSV that is specifically formatted (as required by a vendor). There are four values that are being delimited as follows:
"Name","Description","Tag","IPAddresses"
The list is quite long (and there are ~150 unique names--only 2 in the sample below) but it basically looks like this:
"2B_AppName-Environment","desc","tag","192.168.1.1"
"2B_AppName-Environment","desc","tag","192.168.22.155"
"2B_AppName-Environment","desc","tag","10.20.30.40"
"6G_ServerName-AltEnv","desc","tag","1.2.3.4"
"6G_ServerName-AltEnv","desc","tag","192.192.192.40"
"6G_ServerName-AltEnv","desc","tag","192.168.50.5"
I am hoping for a way in Perl (or sed/awk, etc.) to come up with the following:
"2B_AppName-Environment","desc","tag","192.168.1.1,192.168.22.155,10.20.30.40"
"6G_ServerName-AltEnv","desc","tag","1.2.3.4,192.192.192.40,192.168.50.5"
So basically, the resulting file will APPEND the duplicates to the first match -- there should only be one line per each app/server name with a list of comma-separated IP addresses just like what is shown above.
Note that the "Decription" and "Tag" fields don't need to be considered in the duplication removal/append logic -- let's assume these are blank for the example to make things easier. Also, in the vendor-supplied list, the "Name" entries are all already sorted to be together.
This short Perl program should suit you. It expects the path to the input CSV file as a parameter on the command line and prints the result to STDOUT. It keeps track of the appearance of new name fields in the #names array so that it can print the output in the order that each name first appears, and it takes the values for desc and tag from the first occurrence of each unique name.
use strict;
use warnings;
use Text::CSV;
my $csv = Text::CSV->new({always_quote => 1, eol => "\n"});
my (#names, %data);
while (my $row = $csv->getline(*ARGV)) {
my $name = $row->[0];
if ($data{$name}) {
$data{$name}[3] .= ','.$row->[3];
}
else {
push #names, $name;
$data{$name} = $row;
}
}
for my $name (#names) {
$csv->print(*STDOUT, $data{$name});
}
output
"2B_AppName-Environment","desc","tag","192.168.1.1,192.168.22.155,10.20.30.40"
"6G_ServerName-AltEnv","desc","tag","1.2.3.4,192.192.192.40,192.168.50.5"
Update
Here's a version that ignores any record that doesn't have a valid IPv4 address in the fourth field. I've used Regexp::Common as it's the simplest way to get complex regex patterns right. It may need installing on your system.
use strict;
use warnings;
use Text::CSV;
use Regexp::Common;
my $csv = Text::CSV->new({always_quote => 1, eol => "\n"});
my (#names, %data);
while (my $row = $csv->getline(*ARGV)) {
my ($name, $address) = #{$row}[0,3];
next unless $address =~ $RE{net}{IPv4};
if ($data{$name}) {
$data{$name}[3] .= ','.$address;
}
else {
push #names, $name;
$data{$name} = $row;
}
}
for my $name (#names) {
$csv->print(*STDOUT, $data{$name});
}
I would advise you to use a CSV parser like Text::CSV for this type of problem.
Borodin has already pasted a good example of how to do this.
One of the approaches that I'd advise you NOT to use are regular expressions.
The following one-liner demonstrates how one could do this, but this is a very fragile approach compared to an actual csv parser:
perl -0777 -ne '
while (m{^((.*)"[^"\n]*"\n(?:(?=\2).*\n)*)}mg) {
$s = $1;
$s =~ s/"\n.*"([^"\n]+)(?=")/,$1/g;
print $s
}' test.csv
Outputs:
"2B_AppName-Environment","desc","tag","192.168.1.1,192.168.22.155,10.20.30.40"
"6G_ServerName-AltEnv","desc","tag","1.2.3.4,192.192.192.40,192.168.50.5"
Explanation:
Switches:
-0777: Slurp the entire file
-n: Creates a while(<>){...} loop for each “line” in your input file.
-e: Tells perl to execute the code on command line.
Code:
while (m{^((.*)"[^"]*"\n(?:(?=\2).*\n)*)}mg): Separate text into matching sections.
$s =~ s/"\n.*"([^"\n]+)(?=")/,$1/g;: Join all ip addresses by a comma in matching sections.
print $s: Print the results.
I've got a bunch of data in a CSV file, first row is all strings (all text and underscores), all subsequent rows are filled with numbers relating to said strings.
I'm trying to parse through the first line and find particular strings, remember which column that string was in, and then go through the rest of the file and get the data in the same column. I need to do this to three strings.
I've been using Text::CSV but I can't figure out how to get it to increment a counter until it finds the string in the first line and then go to the next line, get the data from that same column, etc. etc. Here's what I've tried so far:
while (<CSV>) {
if ($csv->parse($data)) {
my #field = $csv->fields;
my $count = 0;
for $column (#field) {
print ++$count, " => ", $column, "\n";
}
} else {
my $err = $csv->error_input;
print "Failed to parse line: $err";
}
}
Since $data is in line 1, it prints "1 $data" 25 times (# of lines in CSV file). How do I get it to remember which column it found $data in? Also, since I know all of the strings are in line 1, how do I get it to only parse through line 1, find all of the strings in #data, and then parse through the rest of the file, grabbing data from the necessary columns and putting it into a matrix or array of arrays?
Thanks for the help!
edit: I realized my questions were a bit poorly phrased. I don't know how to get the column number from CSV. How is this done?
Also, once I've got the column number, how do I tell it CSV to run through the subsequent lines and grab data from only that column?
Try something like this:
use strict;
use warnings;
use Text::CSV;
my $csv = Text::CSV->new({binary=>1});
my $thing_to_match = "blah";
my $matched_index;
my #stored_data = ();
while(my $row= $csv->getline(*DATA)) #grabs lines below __DATA__
#(near the end of the script)
{
my #fields = #$row;
#If we haven't found the matched index, yet, search for it.
if(not defined $matched_index)
{
foreach my $i(0..$#fields)
{
$matched_index = $i if($fields[$i] eq $thing_to_match);
}
}
#NOTE: We're pushing a *reference* to an array!
#Look at perldoc perldata
push #stored_data,\#fields;
}
die "Column for '$thing_to_match' not found!" unless defined $matched_index;
foreach my $row(#stored_data)
{
print $row->[$matched_index] . "\n";
}
__DATA__
stuff,more stuff,yet more stuff
"yes, this thing, is one item",blah,blarg
1,2,3
The output is:
more stuff
blah
2
I don't have time to write up a full example, but I wrote a module that might help you do this. Tie::Array::CSV uses some magic to make your csv file act like a Perl array of arrayrefs. In this way you can use your knowledge of Perl to interact with the file.
A word of warning though! One benefit of my module is that it is read/write. Since you only want read, be careful not to assign to it!
I want to see if I have repeated items in my array, there are over 16.000 so will automate it
There may be other ways but I started with this and, well, would like to finish it unless there is a straightforward command. What I am doing is shifting and pushing from one array into another and this way, check the destination array to see if it is "in array" (like there is such a command in PHP).
So, I got this sub routine and it works with literals, but it doesn't with variables. It is because of the 'eq' or whatever I should need. The 'sourcefile' will contain one or more of the words of the destination array.
// Here I just fetch my file
$listamails = <STDIN>;
# Remove the newlines filename
chomp $listamails;
# open the file, or exit
unless ( open(MAILS, $listamails) ) {
print "Cannot open file \"$listamails\"\n\n";
exit;
}
# Read the list of mails from the file, and store it
# into the array variable #sourcefile
#sourcefile = <MAILS>;
# Close the handle - we've read all the data into #sourcefile now.
close MAILS;
my #destination = ('hi', 'bye');
sub in_array
{
my ($destination,$search_for) = #_;
return grep {$search_for eq $_} #$destination;
}
for($i = 0; $i <=100; $i ++)
{
$elemento = shift #sourcefile;
if(in_array(\#destination, $elemento))
{
print "it is";
}
else
{
print "it aint there";
}
}
Well, if instead of including the $elemento in there I put a 'hi' it does work and also I have printed the value of $elemento which is also 'hi', but when I put the variable, it does not work, and that is because of the 'eq', but I don't know what else to put. If I put == it complains that 'hi' is not a numeric value.
When you want distinct values think hash.
my %seen;
#seen{ #array } = ();
if (keys %seen == #array) {
print "\#array has no duplicate values\n";
}
It's not clear what you want. If your first sentence is the only one that matters ("I want to see if I have repeated items in my array"), then you could use:
my %seen;
if (grep ++$seen{$_} >= 2, #array) {
say "Has duplicates";
}
You said you have a large array, so it might be faster to stop as soon as you find a duplicate.
my %seen;
for (#array) {
if (++$seen{$_} == 2) {
say "Has duplicates";
last;
}
}
By the way, when looking for duplicates in a large number of items, it's much faster to use a strategy based on sorting. After sorting the items, all duplicates will be right next to each other, so to tell if something is a duplicate, all you have to do is compare it with the previous one:
#sorted = sort #sourcefile;
for (my $i = 1; $i < #sorted; ++$i) { # Start at 1 because we'll check the previous one
print "$sorted[$i] is a duplicate!\n" if $sorted[$i] eq $sorted[$i - 1];
}
This will print multiple dupe messages if there are multiple dupes, but you can clean it up.
As eugene y said, hashes are definitely the way to go here. Here's a direct translation of the code you posted to a hash-based method (with a little more Perlishness added along the way):
my #destination = ('hi', 'bye');
my %in_array = map { $_ => 1 } #destination;
for my $i (0 .. 100) {
$elemento = shift #sourcefile;
if(exists $in_array{$elemento})
{
print "it is";
}
else
{
print "it aint there";
}
}
Also, if you mean to check all elements of #sourcefile (as opposed to testing the first 101 elements) against #destination, you should replace the for line with
while (#sourcefile) {
Also also, don't forget to chomp any values read from a file! Lines read from a file have a linebreak at the end of them (the \r\n or \n mentioned in comments on the initial question), which will cause both eq and hash lookups to report that otherwise-matching values are different. This is, most likely, the reason why your code is failing to work correctly in the first place and changing to use sort or hashes won't fix that. First chomp your input to make it work, then use sort or hashes to make it efficient.
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.
I am new to Perl, by the way. I have a Perl script that needs to count the number of times a string appears in the file. The script gets the word from the file itself.
I need it to grab the first word in the file and then search the rest of the file to see if it is repeated anywhere else. If it is repeated I need it to return the amount of times it was repeated. If it was not repeated, it can return 0. I need it to then get the next word in the file and check this again.
I will grab the first word from the file, search the file for repeats of that word, grab the second word from
the file, search the file for repeats of that word, grab the third word from the file, search the file for repeats of that word.
So far I have a while loop that is grabbing each word I need, but I do not know how to get it to search for repeats without resetting the position of my current line. So how do I do this? Any ideas or suggestions are greatly appreciated! Thanks in advance!
while (<theFile>) {
my $line1 = $_;
my $startHere = rindex($line1, ",");
my $theName = substr($line1, $startHere + 1, length($line1) - $startHere);
#print "the name: ".$theName."\n";
}
Use a hashtable;
my %wordcount = ();
while(my $line = <theFile>)
{
chomp($line);
my #words = split(' ', $line);
foreach my $word(#words)
{
$wordCount{$word} += 1;
}
}
# output
foreach my $key(keys %wordCount)
{
print "Word: $key Repeat_Count: " . ($wordCount{$key} - 1) . "\n";
}
The $wordCount{$key} - 1 in the output accounts for the first time a word was seen; Words that only apprear once in the file will have a count of 0
Unless this is actually homework and/or you have to achieve the results in the specific manor you describe, this is going to be FAR more efficient.
Edit: From your comment below:
Each word i am searching for is not "the first word" it is a certain word on the line. Basically i have a csv file and i am skipping to the third value and searching for repeats of it.
I would still use this approach. What you would want to do is:
split on , since this is a CSV file
Pull out the 3rd word in the array on each line and store the words you are interested in in their own hash table
At the end, iterate through the "search word" hash table, and pull out the counts from the wordcount table
So:
my #words = split(',', $line);
$searchTable{#words[2]} = 1;
...
foreach my $key(keys %searchTable)
{
print "Word: $key Repeat_Count: " . ($wordCount{$key} - 1) . "\n";
}
you'll have to adjust according to what rules you have around counting words that repeat in the third column. You could just remove them from #words before the loop that inserts into your wordCount hash.
my $word = <theFile>
chomp($word); #`assuming word is by itself.
my $wordcount = 0;
foreach my $line (<theFile>) {
$line =~ s/$word/$wordcount++/eg;
}
print $wordcount."\n";
Look up the regex flag 'e' for more on what this does. I didn't test the code, but something like it should work. For clarification, the 'e' flag evaluates the second part of the regex (the substitution) as code before replacing, but it's more than that, so with that flag you should be able to make this work.
Now that I understand what you are asking for, the above solution won't work. What you can do, is use sysread to read the entire file into a buffer, and run the same substition after that, but you will have to get the first word off manually, or you can just decrement after the fact. This is because the sysread filehandle and the regular filehandle are handled differently, so try this:
my $word = <theFile>
chomp($word); #`assuming word is by itself.
my $wordcount = 0;
my $srline = '';
#some arbitrary very long length, longer than file
#Looping also possible.
sysread(theFile,$srline,10000000)
$srline =~ s/$word/$wordcount++/eg;
$wordcount--; # I think that the first word will still be in here, causing issues, you should test.
print $wordcount."\n";
Now, given that I read your comment responding to your question, I don't think that your current algorithm is optimal, and you probably want a hash storing up all of the counts for words in a file. This would probably be best done using something like the following:
my %counts = ();
foreach my $line (<theFile>) {
$line =~ s/(\w+)/$counts{$1}++/eg;
}
# now %counts contains key-value pair words for everything in the file.
To find count of all words present in the file you can do something like:
#!/usr/bin/perl
use strict;
use warnings;
my %count_of;
while (my $line = <>) { #read from file or STDIN
foreach my $word (split /\s+/, $line) {
$count_of{$word}++;
}
}
print "All words and their counts: \n";
for my $word (sort keys %count_of) {
print "'$word': $count_of{$word}\n";
}
__END__