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Conference star::wizards

Title:	"ASK THE WIZARDS"

Moderator:	QUARK::LIONEL

Created:	Mon Oct 30 1995
Last Modified:	Mon May 12 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	1857
Total number of notes:	3728

1817.0. "Open: how to use QIO in C" by STAR::JKEENAN () Tue Apr 29 1997 13:57

Date: Thu, 24 Apr 1997 07:45:04 -0400
Message-Id: <[email protected]>
From: "VMS001::WWW"@vms001.das-x.dec.com (24-Apr-1997 0745)
To: [email protected], [email protected], [email protected]
Subject: Ask the Wizard: '[email protected]'

Remote Host: rg5dynamic231.i-way.co.uk
Browser Type: Mozilla/3.01 (X11; I; SunOS 5.5.1 sun4u)
Remote Info: <null>
Name: David Dawkins
Email Address: [email protected]
CPU Architecture: VAX and Alpha
Version: v 6.2
Questions: 

Can you show me (in C) how to use QIO to:

- open a flat text file
- write to it
- read from it
- position the read/write pointer at a specific byte

Please?

T.R Title User Personal
Name Date Lines

1817.1 Please See Documentation; Consider RMS XDELTA::HOFFMAN Steve, OpenVMS Engineering Tue Apr 29 1997 17:43 19

T.R	Title	User	Personal Name	Date	Lines
1817.1	Please See Documentation; Consider RMS	XDELTA::HOFFMAN	Steve, OpenVMS Engineering	`Tue Apr 29 1997 17:43`	19
	There are various examples of using the sys$qio and sys$qiow call in the OpenVMS documentation (specifically in the I/O User's Reference Manual, and in the Programming Concepts Manual), in the sys$examples: area, in the ucx$examples: area, on the freeware CD-ROM, and at various sites around the Internet. The sys$qio (XQP) I/O interface is a very low-level interface, and it bypasses all RMS record structures -- reads and writes are based on the virtual block (block within file) or logical block (block on disk). For obvious reasons, performing virtual operations is prefered by most programmers -- one can corrupt a disk with an errant logical-block I/O. Given your stated goals, I would use RMS -- it is much more flexible, and with a fixed-length sequential file, can perform this task quite easily. Look through the above areas for sys$open, sys$close, etc., and other RMS calls. I would also consider using the C library calls for file I/O operations. (And there are examples of both available.)

   There are various examples of using the sys$qio and sys$qiow call in
   the OpenVMS documentation (specifically in the I/O User's Reference
   Manual, and in the Programming Concepts Manual), in the sys$examples:
   area, in the ucx$examples: area, on the freeware CD-ROM, and at various
   sites around the Internet.

   The sys$qio (XQP) I/O interface is a very low-level interface, and it
   bypasses all RMS record structures -- reads and writes are based on
   the virtual block (block within file) or logical block (block on disk).
   For obvious reasons, performing virtual operations is prefered by most
   programmers -- one can corrupt a disk with an errant logical-block I/O.

   Given your stated goals, I would use RMS -- it is much more flexible,
   and with a fixed-length sequential file, can perform this task quite
   easily.  Look through the above areas for sys$open, sys$close, etc.,
   and other RMS calls.  I would also consider using the C library calls
   for file I/O operations.  (And there are examples of both available.)