lock

Remonter à Io.h - Index

Header File

io.h

Category

Input/output Routines

Prototype

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

Description

Sets file-sharing locks.

lock provides an interface to the operating system file-sharing mechanism.

A 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

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++
	+