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Full Discussion: question on redirection (<<)
Top Forums Shell Programming and Scripting question on redirection (<<) Post 302072425 by newkidintown on Tuesday 2nd of May 2006 06:33:20 PM
Old 05-02-2006
question on redirection (<<)

I came across the following problem, where file contents are overwritten using redirection. Can somebody please explain what cat << BAR seems to be doing and say why this is a problem? Explain the contents and relation between the two filenames used before the cat command. thanks


/tmp# echo 'hello world' > rootfile
/tmp# chmod 600 rootfile
/tmp# ln -s rootfile sh$$
/tmp# chown -h 666.666 sh$$
/tmp# ls -l rootfile sh$$
-rw------- 1 root root 12 Oct 29 03:55 rootfile
lrwxrwxrwx 1 666 666 8 Oct 29 03:56 sh12660 -> rootfile
/tmp# cat <<BAR
? FOO
? BAR
FOO
o world
/tmp# ls -l rootfile sh$$
/bin/ls: sh12660: No such file or directory
-rw------- 1 root root 12 Oct 29 03:56 rootfile
/tmp# cat rootfile
FOO
o world
/tmp#
 

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Net::DNS::Question(3)					User Contributed Perl Documentation				     Net::DNS::Question(3)

NAME
Net::DNS::Question - DNS question record SYNOPSIS
use Net::DNS::Question; $question = new Net::DNS::Question('example.com', 'A', 'IN'); DESCRIPTION
A Net::DNS::Question object represents a record in the question section of a DNS packet. METHODS
new $question = new Net::DNS::Question('example.com', 'A', 'IN'); $question = new Net::DNS::Question('example.com'); $question = new Net::DNS::Question('192.0.32.10', 'PTR', 'IN'); $question = new Net::DNS::Question('192.0.32.10'); Creates a question object from the domain, type, and class passed as arguments. One or both type and class arguments may be omitted and will assume the default values shown above. RFC4291 and RFC4632 IP address/prefix notation is supported for queries in both in-addr.arpa and ip6.arpa namespaces. decode $question = decode Net::DNS::Question($data, $offset); ($question, $offset) = decode Net::DNS::Question($data, $offset); Decodes the question record at the specified location within a DNS wire-format packet. The first argument is a reference to the buffer containing the packet data. The second argument is the offset of the start of the question record. Returns a Net::DNS::Question object and the offset of the next location in the packet. An exception is raised if the object cannot be created (e.g., corrupt or insufficient data). encode $data = $question->encode( $offset, $hash ); Returns the Net::DNS::Question in binary format suitable for inclusion in a DNS packet buffer. The optional arguments are the offset within the packet data where the Net::DNS::Question is to be stored and a reference to a hash table used to index compressed names within the packet. qname, zname $qname = $question->qname; $zname = $question->zname; Returns the question name attribute. In dynamic update packets, this attribute is known as zname() and refers to the zone name. qtype, ztype $qtype = $question->qtype; $ztype = $question->ztype; Returns the question type attribute. In dynamic update packets, this attribute is known as ztype() and refers to the zone type. qclass, zclass $qclass = $question->qclass; $zclass = $question->zclass; Returns the question class attribute. In dynamic update packets, this attribute is known as zclass() and refers to the zone class. print $object->print; Prints the record to the standard output. Calls the string() method to get the string representation. string print "string = ", $question->string, " "; Returns a string representation of the question record. COPYRIGHT
Copyright (c)1997-2002 Michael Fuhr. Portions Copyright (c)2002-2004 Chris Reinhardt. Portions Copyright (c)2003,2006-2011 Dick Franks. All rights reserved. This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself. SEE ALSO
perl, Net::DNS, Net::DNS::DomainName, Net::DNS::Packet, RFC 1035 Section 4.1.2 perl v5.16.2 2012-01-27 Net::DNS::Question(3)
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