dflock, dflockw, dfunlock - lock/unlock an RMSfile for exclusive
use
#include
int dflock (fcb)
DFILE *fcb;
int dflockw (fcb)
DFILE *fcb;
int dfunlock (fcb)
DFILE *fcb;
Dflock attempts to lock an RMSfile for exclusive use and returns
immediately with a status code. If the RMSfile was locked
successfully, then dflock returns a positive value. If the
RMSfile could not be locked, perhaps because it was already
locked by another process, a zero value is returned.
Dflockw attempts to lock an RMSfile for exclusive use, and waits
until the entire RMSfile can be locked before returning. Dflockw
normally returns a positive value.
Dfunlock unlocks an RMSfile that was locked using dflock or
dflockw.
Fcb is the file block pointer returned by dlopen(C-3)
or
dopen(C-3).
These routines must be used in a multi-user environment when
calling RMS file functions to prevent simultaneous access to data
by more than one process. The RMS file functions do not
automatically lock files or records to prevent simultaneous
access to data.
drlock(C-3), dclock(C-3),
dilock(C-3), dlopen(C-3),
dopen(C-3)
Chapter 4, RMS Programming Guide
Dflock and Dflockw return a value of zero (0) if fcb is not an
opened file block pointer or if locking the RMSfile would cause a
deadlock.