Question

Perl is continuing to surprise me. I have a code which takes an input from the command line and checks if it is in a file. I have a file like this:

ls

date

pwd

touch

rm

First i read this file as

open(MYDATA,"filename") or die "Can not open file\n";
@commandlist = <MYDATA>;
chomp @commandlist;
close MYDATA;

the argument is in $commandname variable. To check if it is correct i printed to screen.

print $commandname."\n";

it works well. then i write the code.

$count = @commandlist;
for($i=0;$i < $count;$i++)
{
    print $commandname;
    print $commandlist[$i];
    print "\n";
    if($commandname eq $commandlist[$i])
    {
        print "equal\n";
    }
}

and it does not print ‘equal’. but it should do becaues $commandname variable has the value ‘ls’ which is in the file. i also print the value of $commandname and $commandlist[$i] to see if “visibly” they are equal and i get the output:

ls
lsls
lsdate
lspwd
lstouch
lsrm

here i see that they got the same value but why never eq operator evaluates to zero.
Additionally to get this task done, I have tried various methods all of which come to be useless like making a hash from the array and using exists.
I am struggling for this seemingly easy problem for a day but i just dont get it.
Thanks in advance

EDIT:
when i change the above loop as below

$count = @commandlist;
for($i=0;$i < $count;$i++)
{
    print $commandlist[$i];
    print $commandname;
    print "\n";
    if($commandname eq $commandlist[$i])
    {
        print "equal\n";
    }
}

I got an output like.

ls
ls
lste
lsd
lsuch
ls

it seems like for some reason it overwrites some characters.

EDIT:

my whole script is like:

#reading file code, i posted above
while(<>)
chomp($_);
$commandname = $_;
if($commandname eq "start"){
##something here
} elsif ($commandname eq "machines"){
##something here
} else {

    $count = @commandlist;
    for($i=0;$i < $count;$i++)
    {
        print $commandlist[$i];
        print $commandname;
        print "\n";
        if($commandname eq $commandlist[$i])
        {
            print "equal\n";
        }
    }

}

Answer 1

A bit change in the code would result in what you are looking for, “chomp” the string from array before you put it for comparison. Here it is

chomp $commandlist[$i];

if($commandname eq $commandlist[$i])
{
    print "equal\n";
}

EDIT: as per perldoc chomp when you are chomping a list you should parenthesis. So, in your case … instead simply saying

chomp @commandlist 

make it like

chomp(@commandlist)

FINAL EDIT: I tried this and worked fine. Give it a try

$commandname = $ARGV[0];

open(MYDATA,"chk.txt") or die "Can not open file\n"; 
@commandlist = <MYDATA>; 
chomp(@commandlist);
close MYDATA; 

print $commandname."\n"; 

$count = @commandlist;
print $commandname; 
for($i=0;$i < $count;$i++) 
 {

 print $commandlist[$i]; 
 print "\n"; 
 if($commandname eq $commandlist[$i]) 
 {   
  print "equal\n";   
 } 
 }