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Perl: Backslash found where operator expected

Posted on 2014-04-03
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Last Modified: 2014-04-03
Hello expert,

This Perl code works when the path used for the target
file is in the same directory as the Perl executable.
But when I change to a shared drive on the network
   open (MYFILE, '>>I:\Internal_Processes\Service_Now_Discovery\CMDB_data\data2.txt');
I get
Backslash found where operator expected at open_ie4.pl line 18, near "Internal_Processes"
Obviously it doesn't like the the backslashes in the file path but how do I tell it
where the target file is without using backslashes in the file path?

Thanks

Allen

+++++++++++++++complete code+++++++++++++++++++++
  #!/strawberry perl

  use v5.10.0;
use warnings;
#use strict;

# go to url that is the table of servers in ServiceNow configuration    
# read the table into variable $req
 use LWP::UserAgent;
 $ua = LWP::UserAgent->new;
 $req = HTTP::Request->new(GET => 'https://lhphgtst.service-now.com/cmdb_ci_datacenter.do?XML');
 $req->authorization_basic('allen.pitts', 'password');
# write the table into a file on a local disk
   open (MYFILE, '>>I:\Internal_Processes\Service_Now_Discovery\CMDB_data\data2.txt');
 print MYFILE $ua->request($req)->as_string;
  close (MYFILE);
++++++++++++++++++++++end complete code++++++++++++++++++++++++
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Question by:9apit
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4 Comments
 
LVL 28

Expert Comment

by:FishMonger
ID: 39975663
Use forward slashes instead of back slashes.
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Accepted Solution

by:
FishMonger earned 500 total points
ID: 39975694
Additionally,

1) Commenting out the 'use strict; statement is a bad idea.  Ignoring the errors that it would point out is never a good idea.

2a) You should use a lexical var for the filehandle instead of a bareword.

2b) You should use the 3 arg form of open

2c) You should always check the return code of an open call to verify that is was successful and take proper action if it failed.  That normally means adding a 'die' statement which includes the filename and reason it failed.

#!/strawberry perl

use v5.10.0;
use warnings;
use strict;
use LWP::UserAgent;

# go to url that is the table of servers in ServiceNow configuration    
# read the table into variable $req
my $ua = LWP::UserAgent->new;
my $req = HTTP::Request->new(GET => 'https://lhphgtst.service-now.com/cmdb_ci_datacenter.do?XML');
$req->authorization_basic('allen.pitts', 'password');

# write the table into a file on a local disk
my $file = 'I:/Internal_Processes/Service_Now_Discovery/CMDB_data/data2.txt';
open my $MYFILE, '>>', $file or die "failed to open '$file' <$!>";
print $MYFILE $ua->request($req)->as_string;
close ($MYFILE);

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Author Comment

by:9apit
ID: 39975877
Dr. FishMonger,

Awesome answer.

1) Commenting out the 'use strict; statement is a bad idea.  Ignoring the errors that it would point out is never a good idea.
I get this. Sort of reminds of 'option explicit' in VB. It requires that variable be declared.

2a) You should use a lexical var for the filehandle instead of a bareword.
This one took some research
Lexical Variables
Lexical variables are those declared with my.
Lexical variables must be explicitly declared using the my qualifier.
Lexical variables belong to no package so cannot be fully qualified with a package name.
I think 'use strict' also disables the inappropriate use of barewords.
I think a bareword is an undeclared variable or filehandle.
Researched 'package' but could never get a clear explanation of what a package is.

2b) You should use the 3 arg form of open...
Again had to wrap my head around this but found
Three arguments: the filehandle to open or vivify, the mode of the filehandle, and the name of the file.
So in your excellent code: $MYFILE is the filehandle; >> is the mode, append; [could also be >, overwrite, other modes?] and $file is the name and path of the file
or die is a sort elegant way of handling an error

2c) You should always check the return code of an open call
die is a sort elegant way of handling an error

Thanks

Allen in Dallas (Perl noob)
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Author Closing Comment

by:9apit
ID: 39975894
excellent reply
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