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Top Forums UNIX for Dummies Questions & Answers Process Substitution Question? Post 302635383 by Corona688 on Friday 4th of May 2012 06:30:26 PM
Old 05-04-2012
What does echo filename do? It prints the string 'filename'.

What does cat filename do? It reads from the file named filename.

So the 'echo' just prints the path to the pipe it ought to be reading from. cat actually reads from the pipe, and shows the output of the program.
 

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DAR_SLAVE(1)						      General Commands Manual						      DAR_SLAVE(1)

NAME
dar_slave - disk archive slave SYNOPSIS
dar_slave [options] [<path>/]source dar_slave -h dar_slave -V DESCRIPTION
dar_slave reads an archive and listens for dar orders on standard input, sending asked parts of the archive on standard output. Source is the basename of the archive to read. By default, dar_slave uses standard input and output to communicate with a dar process, which may be running on the local host or on a remote host. It is possible to change the behavior of dar_slave to use named pipe instead of standard input and output OPTIONS
-h Displays help usage. -V Displays version information. -i <filename> reads the orders from the named file instead of standard input. In most cases the filename will be a named pipe. -o <filename> sends the data to the named file <filename> instead of standard output. In most cases the filename will be a named pipe. -E <string> string is a command to be launched between slices. See dar(1) man page (same option) for more informations. -Q Do not display any message on stderr when not launched from a terminal (for example when launched from an at job or crontab). Remains that any question to the user will be assumed a 'no' answer, which most of the time will abort the program. -j when virtual memory is exhausted, as user to make room before trying to continue. By default, when memory is exhausted dar aborts. EXIT CODES
dar_slaves exists with the same codes as dar does, see dar(1) man page. SIGNALS
Any signal sent to dar_slave will abort the program immediately, there is no way to have a proper termination before the end of the process SEE ALSO
dar(1), dar_xform(1), dar_manager(1), dar_cp(1) KNOWN BUGS
None actually. AUTHOR
http://dar.linux.free.fr/ Denis Corbin France Europe 3rd Berkeley Distribution JAN 8, 2006 DAR_SLAVE(1)
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