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