DosOpenSem

Bindings:  C, MASM 

This call opens an existing system semaphore that has been created by 
another process. 

 DosOpenSem     (SemHandle, SemName) 
 

 SemHandle (PHSEM) - output 
    Address of the handle of the system semaphore created by DosCreateSem. 
    This handle must be supplied by any requests directed to the same 
    semaphore. 

 SemName (PSZ) - input 
    Address of the name of the system semaphore created by using 
    DosCreateSem. 

 rc (USHORT) - return 
    Return code descriptions are: 

    0         NO_ERROR 
    100       ERROR_TOO_MANY_SEMAPHORES 
    106       ERROR_SEM_USER_LIMIT 
    123       ERROR_INVALID_NAME 
    187       ERROR_SEM_NOT_FOUND 
 
 Remarks 

 A system semaphore that is created by a call to DosCreateSem with 
 NoExclusive=1 specified returns a handle, which the creating process uses 
 to access the semaphore.  Another process that needs to access the 
 semaphore must call DosOpenSem after the semaphore's creation. DosOpenSem 
 merely returns the handle of the semaphore; it does not test or change 
 the value of the semaphore. 

 If a process has access to any semaphores at the time it issues 
 DosExecPgm to start a child process, the new process inherits the handles 
 to these semaphores. However, the new process initially does not own any 
 inherited semaphores, even if the parent process owns them at the time 
 the child process is started. Semaphore ownership is obtained by a 
 successful DosSemRequest call, and only one process can own the semaphore 
 at a time. 

 When the last process that opened a particular semaphore with a 
 DosCreateSem or DosOpenSem request closes its handle with a DosCloseSem 
 request, the semaphore is deleted from memory and must be be redefined by 
 its next user with a call to DosCreateSem.