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Full Discussion: How to evaluate a variable name on LHS of expression?
Top Forums Shell Programming and Scripting How to evaluate a variable name on LHS of expression? Post 302886778 by DJR on Monday 3rd of February 2014 02:41:50 PM
Old 02-03-2014
How to evaluate a variable name on LHS of expression?
I am trying to write a simple function to select values from a database and assign them to variables. It can have any number of arguments sent into it, and I want to assign the value retrieved to a different variable name for each argument sent in. So my code looks something like this:

Code:
function getParms {
for parm
do 
   `$parm`=`db2 +w -x "SELECT PARM_VALUE_TXT FROM ${FRMWRK_DB_SCHEMA}.JOB_PARM WHERE PARM_NM='$parm' WITH UR"`
done 
getParms parm1 parm2 parm3

I know the db2 statement works correctly. If I just run it once and hardocde the lefthand side with a variable name and then echo it out, it is selecting the proper value from the DB and assiging it correctly. But I can't get it to assign it to the parm name I send in. Essentially I need that $parm evaluated first to the parameter name and then used as the LHS of the expression. I have tried every quoting method I know of but can't get it to work. (this is Korn shell)

Thanks.
 

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LEARN ABOUT OSX

putctl

putctl(9F)						   Kernel Functions for Drivers 						putctl(9F)

NAME

       putctl - send a control message to a queue

SYNOPSIS

       #include <sys/stream.h>

       int putctl(queue_t *q, int type);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       q	Queue to which the message is to be sent.

       type	Message type (must be control, not data type).

DESCRIPTION

       putctl()  tests the  type argument to make sure a data type has not been specified, and then attempts to allocate a message block. putctl()
       fails if  type is  M_DATA, M_PROTO, or  M_PCPROTO, or if a message block cannot be allocated. If successful,  putctl() calls  the   put(9E)
       routine of the queue pointed to by  q with the newly allocated and initialized messages.

RETURN VALUES

       On success,  1 is returned. If  type is a data type, or if a message block cannot be allocated, 0 is returned.

CONTEXT

       putctl() can be called from user or interrupt context.

EXAMPLES

       Example 1: Using putctl()

       The   send_ctl()  routine  is  used to pass control messages downstream. M_BREAK messages are handled with  putctl() (line 11). putctl1(9F)
       (line 16) is used for  M_DELAY messages,  so that  parm can be used to specify the length of the delay. In either case, if a message  block
       cannot be allocated  a  variable recording the number of allocation failures
	is incremented (lines 12, 17). If an invalid message type is detected,	cmn_err(9F) panics the system (line 21).

	1  void
	2  send_ctl(wrq, type, parm)
	3      queue_t *wrq;
	4      uchar_t type;
	5      uchar_t parm;
	6  {
	7	  extern int num_alloc_fail;
	8
	9	switch (type) {
       10	  case M_BREAK:
       11	      if (!putctl(wrq->q_next, M_BREAK))
       12		       num_alloc_fail++;
       13		break;
       14
       15	case M_DELAY:
       16	      if (!putctl1(wrq->q_next, M_DELAY, parm))
       17		       num_alloc_fail++;
       18	      break;
       19
       20	default:
       21	      cmn_err(CE_PANIC, "send_ctl: bad message type passed");
       22		break;
       23	  }
       24  }

SEE ALSO

       put(9E), cmn_err(9F), datamsg(9F), putctl1(9F), putnextctl(9F)

       Writing Device Drivers

       STREAMS Programming Guide

SunOS 5.10							    11 Apr 1991 							putctl(9F)
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