A small USV for ALIX boards with i2c support
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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include "logging.h"
int pidfile_create(const char *filename)
{
int fd = open(filename, O_CREAT | O_EXCL | O_RDWR, 0644);
if (fd < 0)
return -1;
char buf[8];
int len = snprintf(buf, sizeof(buf), "%d", getpid());
write(fd, buf, len);
close(fd);
return 0;
}
int pidfile_remove(const char *filename)
{
return unlink(filename);
}
pid_t pidfile_check(const char *filename, int remove_stale)
{
int fd = open(filename, O_RDWR);
if (fd < 0) {
if (errno == ENOENT) {
errno = 0;
return 0;
}
return -1;
}
char buf[9];
int len = read(fd, buf, sizeof(buf) -1);
buf[len] = '\0';
close(fd);
char *tmp;
pid_t pid = strtol(buf, &tmp, 10);
if (len == 0 || tmp == buf)
pid = -1;
/* just return the pid */
if (!remove_stale)
return pid;
/* invalid pid, remove stale file */
if (pid == -1) {
pidfile_remove(filename);
return 0;
}
/* check if pid is still running */
if (kill(pid, 0) == 0 || errno != ESRCH) {
errno = 0;
return pid;
}
errno = 0;
pidfile_remove(filename);
return 0;
}