62 lines
1.2 KiB
C
Executable file
62 lines
1.2 KiB
C
Executable file
#include <lib.h>
|
|
#include <errno.h>
|
|
#include <sys/types.h>
|
|
#include <unistd.h>
|
|
#include <string.h>
|
|
#include <fcntl.h>
|
|
#include <stdio.h>
|
|
#if _ANSI
|
|
#include <stdlib.h>
|
|
#endif
|
|
|
|
typedef enum {
|
|
False, True
|
|
} BOOLEAN;
|
|
|
|
#define LOCKDIR "/tmp/" /* or /usr/tmp/ as the case may be */
|
|
#define MAXTRIES 3
|
|
#define NAPTIME (unsigned int)5
|
|
|
|
PRIVATE _PROTOTYPE( char *lockpath, (char *name));
|
|
_PROTOTYPE( void syserr, (char *errstring));
|
|
_PROTOTYPE( BOOLEAN lock, (char *name));
|
|
_PROTOTYPE( void unlock, (char *name));
|
|
|
|
void
|
|
syserr(errstring)
|
|
char *errstring;
|
|
{
|
|
fprintf(stderr,"couldn't %s\n", errstring);
|
|
exit(1);
|
|
}
|
|
|
|
BOOLEAN lock(name) /* acquire lock */
|
|
char *name;
|
|
{
|
|
char *path;
|
|
int fd, tries;
|
|
|
|
path = lockpath(name);
|
|
tries = 0;
|
|
while ((fd = creat(path, 0)) == -1 && errno == EACCES) {
|
|
if (++tries >= MAXTRIES) return(False);
|
|
sleep(NAPTIME);
|
|
}
|
|
if (fd == -1 || close(fd) == -1) syserr("lock");
|
|
return(True);
|
|
}
|
|
|
|
void unlock(name) /* free lock */
|
|
char *name;
|
|
{
|
|
if (unlink(lockpath(name)) == -1) syserr("unlock");
|
|
}
|
|
|
|
PRIVATE char *lockpath(name) /* generate lock file path */
|
|
char *name;
|
|
{
|
|
PRIVATE char path[20];
|
|
|
|
strcpy(path, LOCKDIR);
|
|
return(strcat(path, name));
|
|
}
|