unlock

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Header File

io.h

Category

Input/output Routines

Prototype

int unlock(int handle, long offset, long length);

Description

Releases file-sharing locks.

unlock provides an interface to the operating system file-sharing mechanism. unlock removes a lock previously placed with a call to lock. To avoid error, all locks must be removed before a file is closed. A program must release all locks before completing.

Return Value

On success, unlock returns 0

O error, it returns -1.

Example

#include <io.h>
#include <fcntl.h>
#include <sys\stat.h>
#include <process.h>
#include <share.h>
#include <stdio.h>
int main(void)
{
   int handle, status;
   long length;
   handle = _sopen("c:\\autoexec.bat",O_RDONLY,SH_DENYNO,S_IREAD);
   if (handle < 0)
   {
       printf("_sopen failed\n");
       exit(1);
   }
   length = filelength(handle);
   status = lock(handle,0L,length/2);
   if (status == 0)
      printf("lock succeeded\n");
   else
      printf("lock failed\n");
   status = unlock(handle,0L,length/2);
   if (status == 0)
      printf("unlock succeeded\n");
   else
      printf("unlock failed\n");
   close(handle);
   return 0;
}

Portability

POSIX	Win32	ANSI C	ANSI C++
	+