Real-time scenarios where VARIABLE SUBSTITUTION/EXPANSION is useful Post: 302946280

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Top Forums Shell Programming and Scripting Real-time scenarios where VARIABLE SUBSTITUTION/EXPANSION is useful Post 302946280 by bakunin on Sunday 7th of June 2015 04:37:12 AM

06-07-2015

Registered User

MadeInGermany, you are right. You are right too in pointing out that ":-" is perhaps more common than ":=". I just used this as - one - example out of a millions applications for parameter expansion in general because the threads o/p has mentioned it explicitly in his post #1.

I didn't undergo too much effort in explaining what a specific expansion could be used for because - see the first part of my answer - i think what sets apart programmers from the non-programmers is the ability to look at a certain language feature (or function, tool, ...) and come up with an idea of its useful application. People who see a certain stone and do not envision a sculpture IMHO do not have what it takes to be a sculptor either.

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rtprio

rtprio(1)						      General Commands Manual							 rtprio(1)

NAME

       rtprio - execute process with real-time priority

SYNOPSIS

       priority command [arguments]

       priority

       command [arguments]

DESCRIPTION

       executes  command  with	a  real-time priority, or changes the real-time priority of currently executing process pid.  Real-time priorities
       range from zero (highest) to 127 (lowest).  Real-time processes are not subject to priority degradation, and are all of	greater  (schedul-
       ing) importance than non-real-time processes.  See rtprio(2) for more details.

       If  is specified instead of a real-time priority, executes command with a timeshare (non-real-time) priority, or changes the currently exe-
       cuting process pid from a possibly real-time priority to a timeshare priority.  The former is useful to spawn a timeshare priority  command
       from a real-time priority shell.

       If  is  not  specified, command is not scheduled, or pid's real-time priority is not changed, if the user is not a member of a group having
       access and is not the user with appropriate privileges.	When changing the real-time priority of a currently executing process, the  effec-
       tive  user  ID of the calling process must be the user with appropriate privileges, or the real or effective user ID must match the real or
       saved user ID of the process to be modified.

RETURN VALUE

       returns exit status 0 if command is successfully scheduled or if pid's real-time priority is successfully changed, 1 if command is not exe-
       cutable	or pid does not exist, and 2 if command (pid) lacks real-time capability, or the invoker's effective user ID is not a user who has
       appropriate privileges, or the real or effective user or the real or effective user ID does not match the real or  saved  user  ID  of  the
       process being changed.

EXAMPLES

       Execute file at a real-time priority of 100:

       Set the currently running process pid 24217 to a real-time priority of 40:

AUTHOR

       was developed by HP.

SEE ALSO

       setprivgrp(1M), getprivgrp(2), rtprio(2).

																	 rtprio(1)