Date: Fri, 8 Sep 2006 09:28:45 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: David King <dking@ketralnis.com> Cc: lassee@kth.se, freebsd-questions@freebsd.org Subject: Re: How do I give 2 parameters to programs in an unix enviroment? Message-ID: <20060908142842.GB30620@dan.emsphone.com> In-Reply-To: <F05BCFC5-60FB-423A-9CFC-4085612D307B@ketralnis.com> References: <45016BBC.8080803@kth.se> <F05BCFC5-60FB-423A-9CFC-4085612D307B@ketralnis.com>
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In the last episode (Sep 08), David King said: > Here's an example using zsh (I assume it's the same using bash, but > different using tcsh or sh): > > diff <(find /usr/local -type f | sort) <(for each in /var/db/pkg/*/ > +CONTENTS; do grep -v '^@' $each; done | sort) > > This does a diff(1) of what /var/db/pkg says that /usr/local should > look like, and what it *really* looks like (note that it would need > some tuning in order to actually be useful, but you get the idea) > > This uses the <() operator. What the <() operator does is create a > named pipe in /tmp, execute the commands contained in the parenthesis > in a subshell, and connect the stdout of the subshell into that named > pipe. So it's sort of like using temp files, but you don't have to > clean up after yourself. There's another, similar operator that does > force it to use temp files, but I can never remember what it is :) > Check the manpages for your shell Just for the archives, The =() operator puts the output to a temp file and returns the filename to the main command. It has to wait for the subshell to finish before running the main command, though. -- Dan Nelson dnelson@allantgroup.com
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