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Full Discussion: Processing a file list via named pipe
Top Forums Shell Programming and Scripting Processing a file list via named pipe Post 302809079 by Scrutinizer on Saturday 18th of May 2013 07:09:28 AM
Old 05-18-2013
Usually named pipes would be used between two processes. The problem I see with this approach is that named pipes are byte oriented. So while you are writing the line oriented file list to the named pipe, the processes will be snatching the bytes off the named pipe and once it is gone, it is gone.

So in other words, those parallel reading processes would garble those file names, and so you would need to use some kind of signaling to synchronize the read operations so that it can only be performed by one process at the time..

Another approach might be to use one named pipe per reading process.
 

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LEARN ABOUT OPENSOLARIS

shift

shift(1)							   User Commands							  shift(1)

NAME

       shift - shell built-in function to traverse either a shell's argument list or a list of field-separated words

SYNOPSIS

   sh
       shift [n]

   csh
       shift [variable]

   ksh
       *shift [n]

   ksh
       +shift [n]

DESCRIPTION

   sh
       The positional parameters from $n+1 ... are renamed $1 ... . If n is not specified, it is assumed to be 1.

   csh
       The  components of argv, or variable, if supplied, are shifted to the left, discarding the first component. It is an error for the variable
       not to be set or to have a null value.

   ksh
       The positional parameters from $n+1 $n+1 ... are renamed $1 ..., default n is 1. The parameter n can  be  any  arithmetic  expression  that
       evaluates to a non-negative number less than or equal to $#.

       On this manual page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

	   1.	  Variable assignment lists preceding the command remain in effect when the command completes.

	   2.	  I/O redirections are processed after variable assignments.

	   3.	  Errors cause a script that contains them to abort.

	   4.	  Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a
		  variable assignment. This means that tilde substitution is performed after the = sign and word splitting and file  name  genera-
		  tion are not performed.

   ksh93
       shift  is  a  shell  special  built-in that shifts the positional parameters to the left by the number of places defined by n, or 1 if n is
       omitted. The number of positional parameters remaining is reduced by the number of places that are shifted.

       If n is specified, it is evaluated as an arithmetic expression to determine the number of places to shift. It is an  error  to  shift  more
       than the number of positional parameters or a negative number of places.

       The following exit values are returned by shift in ksh93:

       0     Successful completion. The positional parameters were successfully shifted.

       >0    An error occurred.

       On this manual page, ksh93(1) commands that are preceded by one or two + are treated specially in the following ways:

	   1.	  Variable assignment lists preceding the command remain in effect when the command completes.

	   2.	  I/O redirections are processed after variable assignments.

	   3.	  Errors cause a script that contains them to abort.

	   4.	  They are not valid function names.

	   5.	  Words, following a command preceded by ++ that are in the format of a variable assignment, are expanded with the same rules as a
		  variable assignment. This means that tilde substitution is performed after the = sign and field splitting and file name  genera-
		  tion are not performed.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       csh(1), ksh(1), ksh93(1), sh(1), attributes(5)

SunOS 5.11							    20 Nov 2007 							  shift(1)
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