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Full Discussion: Issue with writing a pipe
Top Forums Shell Programming and Scripting Issue with writing a pipe Post 303045173 by Scrutinizer on Friday 13th of March 2020 01:44:38 AM
Old 03-13-2020
Hi Sea,

The behaviour of printf and echo are different.

Code:
$ echo This is piped
This is piped

and
Code:
$ echo "This is piped"
This is piped

produce the same output*, but this is not the case for printf
Code:
$ printf "%s\n" This is piped 
This
is
piped

Code:
$ printf "%s\n" "This is piped" 
This is piped

This is why you got the output, since unquoted it produces multiple lines and
read LEFT CENTER RIGHT only reads the first line..


--
* In the first case there are 3 arguments, in the second case there is only one.

--
"%q" is likely not portable.
Also I don't expect it to work as intended, try putting quotes around the output of the variables:
Code:
echo "\"$LEFT\" \"$CENTER\" \"$RIGHT\" :: \"${@}\""

Then printf "%q\n" "This is piped" | printe - produces:
Code:
"This is piped" "" "" :: "This is piped  "


Last edited by Scrutinizer; 03-13-2020 at 02:57 AM..
 

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IO::Pipe(3pm)						 Perl Programmers Reference Guide					     IO::Pipe(3pm)

NAME
IO::Pipe - supply object methods for pipes SYNOPSIS
use IO::Pipe; $pipe = IO::Pipe->new(); if($pid = fork()) { # Parent $pipe->reader(); while(<$pipe>) { ... } } elsif(defined $pid) { # Child $pipe->writer(); print $pipe ... } or $pipe = IO::Pipe->new(); $pipe->reader(qw(ls -l)); while(<$pipe>) { ... } DESCRIPTION
"IO::Pipe" provides an interface to creating pipes between processes. CONSTRUCTOR
new ( [READER, WRITER] ) Creates an "IO::Pipe", which is a reference to a newly created symbol (see the "Symbol" package). "IO::Pipe::new" optionally takes two arguments, which should be objects blessed into "IO::Handle", or a subclass thereof. These two objects will be used for the system call to "pipe". If no arguments are given then method "handles" is called on the new "IO::Pipe" object. These two handles are held in the array part of the GLOB until either "reader" or "writer" is called. METHODS
reader ([ARGS]) The object is re-blessed into a sub-class of "IO::Handle", and becomes a handle at the reading end of the pipe. If "ARGS" are given then "fork" is called and "ARGS" are passed to exec. writer ([ARGS]) The object is re-blessed into a sub-class of "IO::Handle", and becomes a handle at the writing end of the pipe. If "ARGS" are given then "fork" is called and "ARGS" are passed to exec. handles () This method is called during construction by "IO::Pipe::new" on the newly created "IO::Pipe" object. It returns an array of two objects blessed into "IO::Pipe::End", or a subclass thereof. SEE ALSO
IO::Handle AUTHOR
Graham Barr. Currently maintained by the Perl Porters. Please report all bugs to <perlbug@perl.org>. COPYRIGHT
Copyright (c) 1996-8 Graham Barr <gbarr@pobox.com>. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. perl v5.18.2 2013-11-04 IO::Pipe(3pm)
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