Document revision date: 28 June 1999

The OpenVMS operating system includes functions that allow users and programs to determine whether a device is a DECdfs client device.

The following example shows how to determine whether a disk is a DECdfs client device by using a DCL procedure. The procedure returns "TRUE" for a DECdfs client device and "FALSE" for a non-DECdfs client device, as follows:

$ RUN SYS$SYSTEM:DFS$CONTROLDFS> MOUNT .FIN.ADMIN.DIV.WILMER DFS_DISKDFS> EXIT$ IS_IT_DFS_CLIENT = F$GETDVI ("DFS_DISK", "DFS_ACCESS")$ SHOW SYMBOL IS_IT_DFS_CLIENT SYMBOL IS_IT_DFS_CLIENT == "TRUE"$

You can determine if DECdfs has been started on the system by checking for the existence of the communications device, DFSRR0:. The following lexical function returns a value of True if the communications driver has been loaded:

F$GETDVI ("DFSRR0","EXISTS")

If this call returns False, neither the client nor the server is active. A similar call that specifies device DFSS0 will determine if the DECdfs server driver has been loaded.

You can also write your own program code. If you need to identify a DECdfs client device in a program, you can use a similar $GETDVI macro call specifying DVI$_DFS_ACCESS as the item code.

The following example shows another way to determine whether a disk is a DECdfs client device. The example uses the C programming language and the SYS$GETDVIW system service routine.

/* * Example program to say if the specified device is a DFS-served device. * The first command line arg is checked. */ #include <stdio.h> #include <stdlib.h> #include <sdef.h> #include <starlet.h> #include <descrip.h> #include <string.h> #include <dvidef.h> /* Item list structure definition. */ struct item_list { unsigned short int length; /* Item buffer length */ unsigned short int code; /* Item code */ void *address; /* Item buffer address */ long *retlen; /* length returned */ long termin; /* terminator */ }; long device_stat; int main (int argc, char *argv[]) { long status; /* system service return status */ $DESCRIPTOR (devname, ""); /* descriptor for device name */ struct item_list ilist = { 4, DVI$_DFS_ACCESS, /* item list code */ &device_stat, /* ptr to returned value */ 0, 0 }; devname.dsc$a_pointer = argv[1]; /* descriptor points to first arg */ devname.dsc$w_length = strlen (argv[1]); status = sys$getdviw ( 0, 0, &devname, &ilist, 0, 0, 0, 0); if (status != SS$_NORMAL) exit (status); /* unknown device, etc. */ if (device_stat) printf ("true\n"); else printf ("false\n"); exit (1); }

The DECdfs access flag is also maintained in the DEVCHAR2 item. To modify the previous program to test that flag:

1. Add: #include <devdef.h>
2. Change the item list code to: DVI$_DEVCHAR2
3. Change the test of the return value to: if (device_stat & DEV$M_DFS)

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