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The C Users' Group Library 1994 August
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wc-cdrom-cusersgrouplibrary-1994-08.iso
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v_08_04
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8n04086a
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1990-03-20
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*****Listing 2*****
semaphor.c
/* Supported operating systems: UNIX, MS-DOS */
#define UNIX (1)
#define MSDOS (2)
#define HOST UNIX
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#if HOST == UNIX
#define PATHDLM ('/') /* path name delimiter */
#include <fcntl.h> /* open() macro definitions */
#include "syscalkr.h" /* system call declarations */
#include <sys/stat.h> /* file mode macros */
#elif HOST == MSDOS
#define PATHDLM ('\\') /* path name delimiter */
#include <fcntl.h> /* open() macro definitions */
#include <io.h> /* close(), open() declarations */
#include <sys/types.h>
#include <sys/stat.h> /* file mode macros */
#endif
#include "semaphor.h"
/* semaphore set table definition */
static semset_t sst[SEMOPEN_MAX];
/* semlower: lower semaphore */
int semlower(semset_t *ssp, int semno)
{
char path[PATH_MAX + 1];
/* remove semaphore file */
sprintf(path, "%s%cs%d", ssp->semdir, (int)PATHDLM, semno);
if (unlink(path) == -1) {
if (errno == ENOENT) errno = EAGAIN;
return -1;
}
errno = 0;
return 0;
}
/* semraise: raise semaphore */
int semraise(semset_t *ssp, int semno)
{
char path[PATH_MAX + 1];
int fd = 0;
/* create semaphore file */
sprintf(path, "%s%cs%d", ssp->semdir, (int)PATHDLM, semno);
#if HOST == UNIX
fd = open(path, O_WRONLY | O_CREAT, 0);
#elif HOST == MSDOS
fd = open(path, O_WRONLY | O_CREAT, S_IREAD | S_IWRITE);
#endif
if (fd == -1) {
return -1;
}
if (close(fd) == -1) {
return -1;
}
errno = 0;
return 0;
}