SYS V messages: permission denied

[Richard]

I don't recall ever getting a permission denied on a message queue
that I created before. SuSE Linux 8.2, GNU gcc 3.3

This code calls msgget() then msgsnd(), basically cramming messages
into the queue up to the system limit.

If I compile and run it as my (non-root) self, I get a permission
denied on the msgsnd(). If I run it as root, all is well. I don't
get it, although it's probably something simple/stupid.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>

#include <sys/types.h>
#include <sys/msg.h>

extern int errno ;

#define MQKEY 4321

void
bail( char *, int ) ;

typedef struct msg_struct_tag
{
long type ;
int ndx ;
int len ;

} msg_struct ;

msg_struct msg ;

int
main(void)
{
int i, tot = 0, mqh ;

if ( (mqh = msgget( MQKEY, IPC_CREAT )) < 0 )
bail( "msqget()", errno ) ;

msg.type = 1 ;
msg.len = sizeof( msg ) ;

for ( i = 0 ; i < 30000 ; i++ )
{
msg.ndx = i ;
if ( msgsnd( mqh, (const void *)&msg, msg.len, IPC_NOWAIT ) < 0 )
bail( "msgsend()", errno ) ;
else
{
tot += msg.len ;
printf( "Msg %d: Total bytes sent: %d\n", i+1, tot ) ;
}
}
return 0 ;
}

void
bail( char * s, int e )
{
printf( "%s: %s\n", s, strerror( e ) ) ;
exit ( -1 ) ;
}


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[Richard]

[email]rochkind@basepath.com[/email] wrote...

> On Wed, 30 Jul 2003 05:35:15 GMT, Richard <rh310@hotmail.com> wrote:
>

> > I don't recall ever getting a permission denied on a message queue that I
> > created before. SuSE Linux 8.2, GNU gcc 3.3
> >

>
> [snip]
>
> Following based on a quick look... sorry if I missed something:
>
> Looks like the message queue is created with no permissions (you need to OR
> them in with IPC_CREAT). So, if the queue already exists, it can't be
> opened.
>
> Either remove the queue each time, or give yourself some permissions, such
> as at least 0600.

<blush>. Thank you.

I owe you. Least I can do is order your book and read it. :)

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