lock

Sets file-sharing locks.

Defined in header <io.h>

Syntax

#include <io.h>
int lock(int handle, long offset, long length);

Portability

Remarks

lock provides an interface to the DOS 3.x file-sharing mechanism.

lock can be placed on arbitrary, nonoverlapping regions of any file. A program attempting to read or write into a locked region will retry the operation three times. If all three retries fail, the call fails with an error.

Return value

lock returns 0 on success. On error, lock returns -1 and sets the global variable errno to

EACCES Locking violation

See also

• open
• sopen
• unlock

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;
   /* must have DOS SHARE.EXE  loaded for file locking to function */
   handle = sopen("c:\\autoexec.bat" , 0_RDONLY,SH_DENYNO,S_IREAD);
   if (handle < 0)  {
      printf ("sopen failed\n");
      exit(l);
   }
   length = filelength (handle);
   status = lock(handle, 0L,length/2);
   if (status == 0)
   printfC'lock succeeded\n") ;
else
   printfC'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;

Differences from modern implementations

Nothing recorded yet.

Modern references

• Microsoft C runtime (search)

These are search links, not yet checked by hand.

Stable link: /3.1/io.h/lock/ · short form /3.1/lock/