Operating System - OpenVMS의 주제 Re: SYS$QIO and C string termination

SYS$QIO and C string termination

AntBark — Fri, 05 Mar 2004 08:44:14 GMT

Hi
I'm using SYS$QIO to retreive a string from a device - it works fine accept that the 3rd char of the 7 char string is a null(\0) which is the termination of a string in C, so I can't get the whole string. Is there a way I can overcome this?

Re: SYS$QIO and C string termination

Antoniov. — Fri, 05 Mar 2004 09:00:37 GMT

Hello,
I can't understand if 3.rd char is wrong null or if you can read because end string.
In seceond case use memcpy instead strcpy function (you need pass string lenght).
If 1.st case you could post more details.

H.T.H.
@Antoniov

Re: SYS$QIO and C string termination

Ian Miller. — Fri, 05 Mar 2004 09:55:49 GMT

The QIO will read the string irrespective of terminators unless you specify special options (for terminal driver). See I/O status block - will contain number of bytes received. If expected 7 bytes use memcpy to copy the data.

Re: SYS$QIO and C string termination

Stanley F Quayle — Sat, 06 Mar 2004 12:17:11 GMT

The idea that \0 terminates a string is only used by C. The I/O Status Block (IOSB) returns the number of characters written to the string.

You're going to have to keep that size separately, and use functions that don't check for \0 (like memcpy instead of strcpy, as previously suggested).

Allowing nulls in strings is one reason that VMS uses string descriptors -- which is another thing that C doesn't do very well.

Re: SYS$QIO and C string termination

Stanley F Quayle — Tue, 30 Aug 2005 07:23:01 GMT

How about assigning some points to the responses?

Pointer to help on points:
http://forums1.itrc.hp.com/service/forums/helptips.do?#33

Thanks in advance.