Perl - New line in array elements

Shell Programming and Scripting
1

Hello,
I have a comma delimited input feed file. The first field has directory location and the second field has file name.
Ex of input feed:

/export/appl/a,abc*.dat
/export/appl/b,xyz*.dat
/export/appl/c,pmn*.dat

Under each directory, there would be many files like...
.
.
.
abc.200801.dat
abc.200802.dat
abc.200803.dat
abc.200804.dat

I'm writing a perl script, in which part of the logic is to get the stat() of the latest file in the corresponding directory. (in this case I need to get stat() of abc.200804.dat

So, first I'm getting the directory and then chdir to that location and doing a ls -ltr with the wild card file names and storing them in array. Then using $

foreach my $input_var (@i_raw_data)
{
 chop($input_var);
 my ($d_loc,$wild_f_nme)=split(/\,/,$input_var);
 chdir($d_loc);
 my @list_files = `ls -c $wild_f_nme`;  #store all file names
 my $f_nme=$list_files[-1];    #it will have latest modified filename

 my ($accesstime, $modtime, $createtime, $fsize) = (stat($f_nme))[8,9,10,7];

The problem is, I think when I'm trying to get the last changed file into the array element, its storing the latest file in the last element, but I think its appending new line to the element along with file name. So, the stat($f_nme) isn't working.

Can you please let me know what I'm missing?
Thanks!

2

Evaluating backticks in list context, Perl does not automatically drop the newlines from the command output for you. You should do that yourself.

Compare the following two cases:

[bernardchan@bernardchan ~]$ perl -MData::Dumper -e '@lines = `ls /usr/local`; print Dumper(\@lines)'
$VAR1 = [
          'Adobe
',
          'apps
',
          'bin
',
          'Brother
',
          'etc
',
          'games
',
          'include
',
          'lib
',
          'libexec
',
          'man
',
          'RealPlayer
',
          'sbin
',
          'share
',
          'src
'
        ];
[bernardchan@bernardchan ~]$ perl -MData::Dumper -e '@lines = map { chomp; $_ } (`ls /usr/local`); print Dumper(\@lines)'
$VAR1 = [
          'Adobe',
          'apps',
          'bin',
          'Brother',
          'etc',
          'games',
          'include',
          'lib',
          'libexec',
          'man',
          'RealPlayer',
          'sbin',
          'share',
          'src'
        ];

As you can see, there are trailing newline with the first case, but not after post-processing each item removing the trailing newlines.

3

Basically what he said... Use chomp($f_nme[-1]) first, then assign it. Use chomp() above where you get the directory list from your input file too... Is safer. chop() will strip the last char of a string ALWAYS. chomp() strips only if is a LINE ENDING, so is much safer usually if you are not always SURE that the last char of your string is the line ending you want to remove....

4

I should have mentioned it.... I've used both chomp($list_files[-1]) and chop($list_files[-1]). It doesn't seem to work.

my $f_nme=chomp($list_files[-1]); 
print " last file name is $f_nme \n";

It doesn't assign any value to $f_nme.

And chomp(($list_files[-1]) returns "1" ?!

foreach my $input_var (@i_raw_data)
{
 chop($input_var);
 my ($d_loc,$wild_f_nme)=split(/\,/,$input_var);
 chdir($d_loc);
 my @list_files = `ls -c $wild_f_nme`;  #store all file names
 my $f_nme=chomp($list_files[-1]);    #it will have latest modified filename

 my ($accesstime, $modtime, $createtime, $fsize) = (stat($f_nme))[8,9,10,7];

Anyways, I have used the way cbhikong suggested and it worked. Thanks!

5

Yes, you misunderstand chomp() chop(). They actually transform their argument. What they RETURN is a 1 or 0 (I think)...

So $y = chop($x); actually changes $x and assigns 1 (success) to $y. So you don't ASSIGN the results, you just do it....

$x = "abcd";

chop($x);

Now $x is "abc"