Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Greetings Perl Monks I have a problem which I'm struggling with due to my limited perl knowledge, which I hope you can assist me with.

I have a string which Dumper displays like this 

$VAR1 = [
          " echo      ",
          " ----------",
          " REPVersion",
          "",
          " Version                                                   
+                                                                     
+               ",
          " ----------------------------------------------------------
+---------------------------------------------------------------------
+---------------",
          " Replication Server/16.0/EBF 27617 SP03 PL03 rs160sp03pl03/
+Linux AMD64/Linux 2.6.32.59-0.19-default x86_64/2214/OPT64/Tue Dec 19
+ 19:00:15 2017 ",
          " echo       ",
          " -----------",
          " REPErrorlog",
          "",
          " Log File Name                                           ",
          " --------------------------------------------------------",
          " /logdisk/logs/my.log",
          " echo          ",
          " --------------",
          " REPSiteVersion",
          "",
          " Site Version",
          " ------------",
          "      1600302",
          " echo       ",
          " -----------",
          " REPRSSDName",
          "",
          " RSSD Dataserver           RSSD Database     ",
          " ------------------------- ------------------",
          " SYBASE_APP123_MYRSSD_SERV SYBASE_APP123_RSSD",
          " ------------",
          " REPQueueSize",
          "",
          "            ",
          " -----------",
          "      102396",
          "                ",
          " ---------------",
          " REPLossDetected",
          "",
          "            ",
          " -----------",
          "           0",
          "              ",
          " -------------",
          " REPSSLEnabled",
          "",
          "            ",
          " -----------",
          "           0"
        ]; 

ARRAY(0x20794b0)

[download]

I'm trying to remove the leading whitespace using this code 

my $result = runDBsql($server,$user,$pass); # Cannot modify runDBsql

remove_leadspace($result);
local $Data::Dumper::Useqq = 1;# In case it is not whitespace but some
+ other character 
print Dumper($result);
print "\n$result\n"; # added for further debugging

sub remove_leadspace
{
    return if not defined wantarray;
    return map { s/^\s+//r } @_ if wantarray;
    return shift =~ s/^\s+//r;
}

[download]

The remove_leadspace is not removing the leftmost spaces

So when I consequently use the returned data which I reference using $result->[n] it looks like this

(' REPErrorlog', ' /logdisk/logs/my.log')
(' REPSiteVersion', '      1600302')
(' REPRSSDName', ' SYBASE_APP123_MYRSSD_SERV SYBASE_APP123_RSSD')
(' REPQueueSize', '      102396')
(' REPLossDetected', '           0')
(' REPSSLEnabled', '           0')

[download]

I inherited this code and I think I'm confusing scalar and array strings.

How do I get rid of the leading whitespace ?

Any help much appreciated

Replies are listed 'Best First'.
Re: Problems removing leading whitespace
by haukex (Archbishop) on Jan 30, 2020 at 11:54 UTC 
    print Dumper($result);
$VAR1 = [
          " echo      ",
          " ----------",
          ...

    [download]

    $result is a reference to an array of strings. You can access the actual array via @$result (perlreftut, perlref). You can simply use this to remove the leading whitespace from all the elements of $result: s/^\s+// for @$result;

    Update: Also, your sub remove_leadspace is designed to return a modified list of strings, but you're not doing anything with its return value. You could do: @$result = remove_leadspace(@$result); or my @trimmed = remove_leadspace(@$result);

[reply]
[d/l]
[select]

      Expanding on this:

      In the original implementation, you call remove_leadspace() without assigning its result to anything. This means that wantarray is undef, so the original implementation of remove_leadspace() returns without doing anything.

      Because in Perl there is More Than One Way To Do It, another implementation would be something like:

      sub remove_leadspace(
    s/^\s+// for @{ $_[0] };
    return;
}

      [download]

      This is called by remove_leadspace( $result ). That is, it expects a single argument which is an array reference, modifies the elements of the array (note that the /r qualifier qas removed from the s///), and returns nothing.

[reply]
[d/l]
[select]

      Fantastic, many thanks for the prompt reply

[reply]

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