Question

I have this Perl code that is only printing the first line instead of all the lines.

use Net::SSH::Perl;
my $user = "user"; 
my $cmd = "df -m | grep data";
my $host = "host1.example.com"; 

my $ssh = Net::SSH::Perl->new($host);
$ssh->login($user);
my ($dflines,$errors,$exit) = $ssh->cmd($cmd);
foreach $line ($dflines) {
  print "$line";
  my @values = split(' ',$line);
  my ($MBsize, $MBused, $MBavail, $dir) =
      ($values[1], $values[2], $values[3], $values[5]);
  print "MBsize=$MBsize MBused=$MBused MBavail=$MBavail dir=$dir\n";
}

It prints:

/dev/sdb1              1407118    931813    403828  70% /data1
/dev/sdc1              1407118    921739    413902  70% /data2
/dev/sdd1              1407118    909408    426233  69% /data3
/dev/sde1              1407118    918828    416813  69% /data4
/dev/sdf1              1407118    922335    413306  70% /data5
MBsize=1407118 MBused=931813 MBavail=403828 dir=/data1

I would expect:

/dev/sdb1              1407118    931813    403828  70% /data1
/dev/sdc1              1407118    921739    413902  70% /data2
/dev/sdd1              1407118    909408    426233  69% /data3
/dev/sde1              1407118    918828    416813  69% /data4
/dev/sdf1              1407118    922335    413306  70% /data5
MBsize=1407118 MBused=931813 MBavail=403828 dir=/data1
MBsize=1407118 MBused=921739 MBavail=413902 dir=/data2
MBsize=1407118 MBused=909408 MBavail=426233 dir=/data3
MBsize=1407118 MBused=918828 MBavail=416813 dir=/data4
MBsize=1407118 MBused=922335 MBavail=413306 dir=/data5

I’m almost certain it’s something basic.
Any help is appreciated.
Thanks!

Answer 1

The problem is this line:

foreach $line ($dflines) {

You are only executing one iteration, since that is not an array, but a scalar. When you print "$line" it actually prints all of the lines that you captured, but I guess it looks like you printed many values in a loop. In the subsequent part:

my @values = split(' ',$line);
my ($MBsize, $MBused, $MBavail, $dir) = 
        ($values[1], $values[2], $values[3], $values[5]);
print "MBsize=$MBsize MBused=$MBused MBavail=$MBavail dir=$dir\n";

You only use the first few values of the split, but the rest of that line is in there as well. In other words, @values contains all of the values you expect. Range 0..5 contains the first row, 6..10 the next, and so on. Since you only use the first 6 values, you don’t see them.

A quick fix might be to do:

foreach $line (split /\n/, $dflines) {

Which would break up your input the way you were expecting it to be.

Some tips:

Always use warnings; use strict;

And you should make use of some proper perl features:

for my $line (split /\n/, $dflines) {
   print $line;
   my @values = split ' ', $line;
   printf "MBsize=%s MBused=%s MBavail=%s dir=%s\n", @values[1,2,3,5];
}

It looks like you want to print the MBsize ... lines after the regular output. If so, you can just store the lines in an array and print after the loop:

my @print;
for my $line (split /\n/, $dflines) {
   print $line;
   my @values = split ' ', $line;
   push @print, sprintf "MBsize=%s MBused=%s MBavail=%s dir=%s\n", @values[1,2,3,5];
}   # note  ----^ sprintf instead
print @print;