Re: [PATCH 2/3] slcand: add option -p<file> to write pid to a file.

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 06/08/2015 01:55 PM, Armin Burchardt wrote:
> Useful in combination with start-stop-daemon.
> 
> Signed-off-by: Armin Burchardt <armin@uni-bremen.de>
> ---
>  slcand.c | 36 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/slcand.c b/slcand.c
> index af7ca98..8fd1418 100644
> --- a/slcand.c
> +++ b/slcand.c
> @@ -64,11 +64,13 @@ void print_usage(char *prg)
>  	fprintf(stderr, "         -t <type>  (set UART flow control type 'hw' or 'sw')\n");
>  	fprintf(stderr, "         -b <btr>   (set bit time register value)\n");
>  	fprintf(stderr, "         -F         (stay in foreground; no daemonize)\n");
> +	fprintf(stderr, "         -p <file>  (write PID of daemon to file)\n");
>  	fprintf(stderr, "         -h         (show this help page)\n");
>  	fprintf(stderr, "\nExamples:\n");
>  	fprintf(stderr, "slcand -o -c -f -s6 ttyUSB0\n");
>  	fprintf(stderr, "slcand -o -c -f -s6 ttyUSB0 can0\n");
>  	fprintf(stderr, "slcand -o -c -f -s6 /dev/ttyUSB0\n");
> +	fprintf(stderr, "slcand -o -c -f -s6 -p/var/run/slcand-can0.pid /dev/ttyUSB0\n");

I think "/run/slcand/<IFACE>" would fit better into modern file system
layout. What about having a default for the pid file path?

>  	fprintf(stderr, "\n");
>  	exit(EXIT_FAILURE);
>  }
> @@ -178,12 +180,13 @@ int main(int argc, char *argv[])
>  	char *btr = NULL;
>  	int run_as_daemon = 1;
>  	char *pch;
> +	char *pidfile = NULL;
>  	int ldisc = N_SLCAN;
>  	int fd;
>  
>  	ttypath[0] = '\0';
>  
> -	while ((opt = getopt(argc, argv, "ocfs:S:t:b:?hF")) != -1) {
> +	while ((opt = getopt(argc, argv, "ocfs:S:t:b:p:?hF")) != -1) {
>  		switch (opt) {
>  		case 'o':
>  			send_open = 1;
> @@ -228,6 +231,9 @@ int main(int argc, char *argv[])
>  		case 'F':
>  			run_as_daemon = 0;
>  			break;
> +		case 'p':
> +			pidfile = optarg;
> +			break;
>  		case 'h':
>  		case '?':
>  		default:
> @@ -363,6 +369,27 @@ int main(int argc, char *argv[])
>  		signal(SIGTERM, child_handler);
>  	}
>  
> +	/* write pidfile */
> +	if (pidfile) {
> +		FILE *pidfd;
> +		pidfd = fopen(pidfile, "w");
> +		if (pidfd == NULL) {

if (!pidfd)

Does it make sense to open in exclusive mode?

Technically speaking, it's not a file descriptor "fd" :)

> +			syslog(LOG_ERR, "could not open pidfile");
> +			perror(pidfile);
> +			exit(EXIT_FAILURE);
> +		}
> +		if (fprintf(pidfd, "%i\n", getpid()) < 0) {
> +			syslog(LOG_ERR, "could not write to pidfile");
> +			perror(pidfile);
> +			exit(EXIT_FAILURE);
> +		}
> +		if (fclose(pidfd) != 0) {
> +			syslog(LOG_ERR, "could not close pidfile");
> +			perror(pidfile);
> +			exit(EXIT_FAILURE);
> +		}
> +	}
> +
>  	/* */
>  	slcand_running = 1;
>  
> @@ -391,6 +418,13 @@ int main(int argc, char *argv[])
>  	if (tcsetattr(fd, TCSADRAIN, &tios) < 0)
>  		syslog(LOG_NOTICE, "Cannot set attributes for device \"%s\": %s!\n", ttypath, strerror(errno));
>  
> +	/* Remove pidfile */
> +	if (pidfile) {
> +		if (unlink(pidfile) < 0) {
> +			syslog(LOG_ERR, "Can not remove pidfile '%s': %s", pidfile, strerror(errno));
> +		}
> +	}
> +
>  	/* Finish up */
>  	syslog(LOG_NOTICE, "terminated on %s", ttypath);
>  	closelog();
> 

Marc

-- 
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