logger: add support for -I PID to log, e.g., $$ from a shell script

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

man/logger.1

@@ -38,6 +38,7 @@
 .Op Fl f Ar FILE
 .Op Fl h Ar HOST
 .Op Fl H Ar HOSTNAME
+.Op Fl I Ar PID
 .Op Fl m Ar MSGID
 .Op Fl p Ar PRIO
 .Op Fl P Ar PORT
@@ -105,6 +106,16 @@ will be used.
 Send the message to the remote system
 .Ar host
 instead of logging it locally.
+.It Fl I Ar PID
+Like
+.Fl i ,
+but uses
+.Ar PID .
+Useful when logging from shell scripts that send multiple messages.
+E.g., the following arguments might be a useful template:
+.Bd -literal -offset indent
+logger -t $(basename $0) -I $$
+.Ed
 .It Fl i
 Log the process id of the logger process with each line
 .Ql ( LOG_PID ) .

src/logger.c

@@ -238,6 +238,7 @@ static int usage(int code)
 	       "  -h HOST   Send (UDP) message to this remote syslog server (IP or DNS name)\n"
 	       "  -H NAME   Use NAME instead of system hostname in message header\n"
 	       "  -i        Log process ID of the logger process with each line (LOG_PID)\n"
+	       "  -I PID    Log process ID using PID, recommed using PID $$ for shell scripts\n"
 #ifdef __linux__
 	       "  -k        Log to kernel /dev/kmsg if /dev/log doesn't exist yet\n"
 #endif
@@ -278,7 +279,7 @@ int main(int argc, char *argv[])
 	int c, num = 5;
 	int rotate = 0;
 
-	while ((c = getopt(argc, argv, "46?bcd:f:h:H:ikm:np:P:r:st:u:v")) != EOF) {
+	while ((c = getopt(argc, argv, "46?bcd:f:h:H:iI:km:np:P:r:st:u:v")) != EOF) {
 		switch (c) {
 		case '4':
 			family = AF_INET;
@@ -316,6 +317,11 @@ int main(int argc, char *argv[])
 			log_opts |= LOG_PID;
 			break;
 
+		case 'I':
+			log_opts |= LOG_PID;
+			log.log_pid = atoi(optarg);
+			break;
+
 		case 'k':
 #ifdef __linux__
 			allow_kmsg = 1;

src/syslog.c

@@ -299,7 +299,9 @@ vsyslogp_r(int pri, struct syslog_data *data, const char *msgid,
 		DEC();
 
 		if (data->log_stat & LOG_PID) {
-			prlen = snprintf(p, tbuf_left, "[%d]", getpid());
+			if (data->log_pid == -1)
+				data->log_pid = getpid();
+			prlen = snprintf(p, tbuf_left, "[%d]", data->log_pid);
 			DEC();
 		}
 		strlcat(p, ":", tbuf_left);
@@ -368,7 +370,9 @@ vsyslogp_r(int pri, struct syslog_data *data, const char *msgid,
 	DEC();
 
 	if (data->log_stat & LOG_PID) {
-		prlen = snprintf(p, tbuf_left, "%d ", getpid());
+		if (data->log_pid == -1)
+			data->log_pid = getpid();
+		prlen = snprintf(p, tbuf_left, "%d ", data->log_pid);
 		if (data->log_stat & (LOG_PERROR|LOG_CONS|LOG_NLOG)) {
 			iov[iovcnt].iov_base = __UNCONST("[");
 			iov[iovcnt].iov_len = 1;

src/syslog.h

@@ -208,6 +208,7 @@ struct syslog_data {
 	int	log_fac;
 	int	log_mask;
 	void	*log_host;		/* struct sockaddr* */
+	int     log_pid;
 };
 
 #define SYSLOG_DATA_INIT { \
@@ -222,6 +223,7 @@ struct syslog_data {
     .log_fac = LOG_USER, \
     .log_mask = 0xff, \
     .log_host = NULL, \
+    .log_pid = -1, \
 }
 
 #ifdef __cplusplus