_lock_file
Visual Studio 2005
Locks a file, preventing other processes from accessing the file.
void _lock_file( FILE* file );
Parameters
- file
-
File handle.
The _lock_file function locks the file specified by file. Locking a file prevents access to the file by other processes. Use _unlock_file to release the lock on the file. Calls to _lock_file and _unlock_file must be matched in a thread. Attempting to lock a file that is already locked or unlock a file that is not locked can result in a deadlock.
| Routine | Required header | Compatibility |
|---|---|---|
| _lock_file | <stdio.h> | Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 |
For more compatibility information, see Compatibility in the Introduction.
// crt_lock_file.c
// This program will Lock a file,
// preventing other processes or threads
// from gaining access to the file until
// it's unlocked.
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE *pFile = NULL;
char *fileName = "crt_lock_file.txt";
char commandLine[256];
// Open the file in write mode
fopen_s(&pFile, fileName ,"w+");
if (!pFile)
{
printf("Error opening file %s!\n", fileName);
exit(1);
}
// Lock the file.
_lock_file(pFile);
printf("Locking the file %s.\n", fileName);
// Add some data to the file
fprintf(pFile, "The sound of bagpipes in the distant glen...\n");
printf("\nAttempting to access the file from another process:\n");
sprintf_s(commandLine, sizeof(commandLine), "type %s", fileName);
system(commandLine);
// Unlock the file
_unlock_file(pFile);
// Close the file
fclose(pFile);
printf("\nAttempting to access the file again:\n");
system(commandLine);
}
Sample Output
Locking the file crt_lock_file.txt. Attempting to access the file from another process: The process cannot access the file because it is being used by another process. Attempting to access the file again: The sound of bagpipes in the distant glen...
