This code outputs the scalars in the row array properly:
$line = "This is my favorite test";
#row = split(/ /, $line);
print $row[0];
print $row[1];
The same code inside a foreach loop doesn't print any scalar values:
foreach $line (#lines){
#row = split(/ /, $line);
print $row[0];
print $row[1];
}
What could cause this to happen?
I am new to Perl coming from python. I need to learn Perl for my new position.
As already mentioned in Jefromi's comments, whatever the problem is, it exists outside of the code you posted. This works entirely fine:
$lines[0] = "This is my favorite test";
foreach $line (#lines) {
#row = split(/ /, $line);
print $row[0];
print $row[1];
}
The output is Thisis
When I run into these sorts of problems where I wonder why something in a block is not happening, I add some debugging code to ensure I actually enter the block:
print "\#lines has " . #lines . " elements to process\n";
foreach my $line ( #lines )
{
print "Processing [$line]\n";
...;
}
You can also do this in your favorite debugger by setting breakpoints and inspecting variables, but that's a bit too much work for me. :)
If you need to learn Perl and already know Python, you shouldn't have that much trouble going through Learning Perl in a couple of days.
Related
When I run this code, I am purely trying to get all the lines containing the word "that" in them. Sounds easy enough. But when I run it, I get a list of matches that contain the word "that" but only at the end of the line. I don't know why it's coming out like this and I have been going crazy trying to solve it. I am currently getting an output of 268 total matches, and the output I need is only 13. Please advise!
#!/usr/bin/perl -w
#Usage: conc.shift.pl textfile word
open (FH, "$ARGV[0]") || die "cannot open";
#array = (1,2,3,4,5);
$count = 0;
while($line = <FH>) {
chomp $line;
shift #array;
push(#array, $line);
$count++;
if ($line =~ /that/)
{
$output = join(" ",#array);
print "$output \n";
}
}
print "Total matches: $count\n";
Don't you want to increment your $count variable only if the line contains "that", i.e.:
if ($line =~ /that/) {
$count++;
instead of incrementing the counter before checking if $line contains "that", as you have it:
$count++;
if ($line =~ /that/) {
Similarly, I suspect that your push() and join() calls, for stashing a matching line in #array, should also be within the if block, only executed if the line contains "that".
Hope this helps!
I've initialized a hash with Names and their class ranking as follows
a=>5,b=>2,c=>1,d=>3,e=>5
I've this code so far
my %Ranks = reverse %Class; #As I need to find out who's ranked first
print "\nFirst place goes to.... ", $Ranks{1};
The code only prints out
"First place goes to...."
I want it to print out
First place goes to....c
Could you tell me where' I'm going wrong here?
The class hash prints correctly
but If I try to print the reversed hash using
foreach $t (keys %Ranks) {
print "\n $t $Ranks{$t}"; }
It prints
5
abc23
cab2
ord
If this helps in any way
FULL CODE
#Script to read from the data file and initialize it into a hash
my %Code;
my %Ranks;
#Check whether the file exists
open(fh, "Task1.txt") or die "The File Does Not Exist!\n", $!;
while (my $line = <fh>) {
chomp $line;
my #fields = split /,/, $line;
$Code{$fields[0]} = $fields[1];
$Class{$fields[0]} = $fields[2];
}
close(fh);
#Prints the dataset
print "Code \t Name\n";
foreach $code ( keys %Code) {
print "$code \t $Code{$code}\n";
}
#Find out who comes first
my %Ranks = reverse %Class;
foreach $t (keys %Ranks)
{
print "\n $t $Ranks{$t}";
}
print "\nFirst place goes to.... ", $Ranks{1}, "\n";
When you want to check what your data structures actually contain, use Data::Dumper. use Data::Dumper; local $Data::Dumper::Useqq = 1; print(Dumper(\%Class));. You'll find un-chomped newlines.
You need to use chomp. At present your $fields[2] value has a trailing newline.
Change your file read loop to this
while (my $line = <fh>) {
chomp $line;
my #fields = split /,/, $line;
$Code{$fields[0]} = $fields[1];
$Class{$fields[0]} = $fields[2];
}
This program doesn't print that the strings are equal but when they get printed, they appear to be the same...someone please explain
#!/usr/bin/perl
$str = "print \"I want this to work\\n\";";
print $str."\n";
open FILE, "<", "check2.doc" or die "buhuhuhu";
my $str2;
while (<FILE>) {
$str2 = $_;
}
close FILE;
print "$str2\n";
if ( $str eq $str2) {
print "they are equal\n";
But when the output comes there is this extra line at the bottom due to the second string $str2
print "I want this to work\n";
print "I want this to work\n";
-----empty line-----
Here is the file check2.doc
print "I want this to work\n";
Does anyone know why they are not equal???
The file read includes the \n, so you have to remove it:
$str2 = $_;
chomp $str2;
And, if your file has only one line, replace the while loop by:
$str2 = <FILE>;
chomp $str2;
The line in the file is created by
$str."\n"
Of course that's not equal to
$str
You need to remove the trailing newline.
my $str2 = <FILE>;
chomp($str2);
I am trying to read a config file and discard the directories that are listed in there with size mentioned in the file. So far I have this-
open FILE, 'C:\reports\config.txt' or die $!;
my $size_req;
my $path;
my $sub_dir;
my $count;
my #lines = <FILE>;
foreach $_ (#lines)
{
my #line = split /\|/, $_;
if ($line[0] eq "size")
{
$size_req= $line[1];
$size_req= ">".$size_req*1024;;
}
if ($line[0] eq "path")
{
$path= $line[1];
}
if ($line[0] eq "directories")
{ my $aa;
my $siz_two_digit;
my $sub_dir;
my $i;
my $array_size=#line;
**for($i=1; $i < $array_size; )**
{
$sub_dir=$line[$i];
print $sub_dir;
print "\n";
print $path;
print "\n";
my $r1 = File::Find::Rule->directory
->name($sub_dir)
->prune # don't go into it
->discard; # don't report it
my $fn = File::Find::Rule->file
->size( $size_req );
my #files = File::Find::Rule->or( $r1, $fn )
->in( $path);
print #files;
undef #files;
print #files;
$i++;
print "\n";
print "\n";
}
}
}
The problem with the for loop is that- it stores all the subdirectories to be discarded from an array just fine. However, when it reads the name of the first directory to be discarded, it does not know about the remaining subdirectories and lists them too. When it goes to the 2 nd value, it ignores the previous one and lists that as well.
Does anyone know if the File|::Find::Rule takes an array at a time so that the code will consider entire line in the configuration file at once? or any other logic?
Thank you
This code does not do what you think:
my $r1 = File::Find::Rule->directory
->name($sub_dir)
->prune # don't go into it
->discard; # don't report it
You are trying to store a rule in a scalar, but what you are actually doing is calling Find::File::Rule and converting the resulting list to an integer (the number of elements in the list) and storing that in $r1.
Just put the whole call in the #files call. It may look messy but it will work a whole lot better.
I am creating a perl script that takes in the a file (example ./prog file)
I need to parse through the file and search for a string. This is what I thought would work, but it does not seem to work. The file is one work per line containing 50 lines
#array = < >;
print "Enter the word you what to match\n";
chomp($match = <STDIN>);
foreach $line (#array){
if($match eq $line){
print "The word is a match";
exit
}
}
You're chomping your user input, but not the lines from the file.
They can't match; one ends with \n the other does not. Getting rid of your chomp should solve the problem. (Or, adding a chomp($line) to your loop).
$match = <STDIN>;
or
foreach $line (#array){
chomp($line);
if($match eq $line){
print "The word is a match";
exit;
}
}
Edit in the hope that the OP notices his mistake from the comments below:
Changing eq to == doesn't "fix" anything; it breaks it. You need to use eq for string comparison. You need to do one of the above to fix your code.
$a = "foo\n";
$b = "bar";
print "yup\n" if ($a == $b);
Output:
yup