Use switch with fork()

Allows dropping a local variable if the explicit PID is not needed
and it makes it clearer what happens.
Also, one should always strive for consistency for cases like these.

cron.c

@@ -102,20 +102,20 @@ runjob(char *cmd)
 		}
 	}
 
-	pid = fork();
-	if (pid < 0) {
+	switch ((pid = fork())) {
+	case -1:
 		logerr("error: failed to fork job: %s time: %s",
 		       cmd, ctime(&t));
 		return;
-	} else if (pid == 0) {
+	case 0:
 		setsid();
 		loginfo("run: %s pid: %d at %s",
 			cmd, getpid(), ctime(&t));
 		execl("/bin/sh", "/bin/sh", "-c", cmd, (char *)NULL);
-		logerr("error: failed to execute job: %s time: %s",
+		logwarn("error: failed to execute job: %s time: %s",
 		       cmd, ctime(&t));
 		_exit(1);
-	} else {
+	default:
 		je = emalloc(sizeof(*je));
 		je->cmd = estrdup(cmd);
 		je->pid = pid;

tar.c

@@ -47,17 +47,16 @@ static char filtermode;
 static FILE *
 decomp(FILE *fp)
 {
-	pid_t pid;
 	int   fds[2];
 
 	if (pipe(fds) < 0)
 		eprintf("pipe:");
 
-	pid = fork();
-	if (pid < 0) {
+	switch (fork()) {
+	case -1:
 		weprintf("fork:");
 		_exit(1);
-	} else if (!pid) {
+	case 0:
 		dup2(fileno(fp), 0);
 		dup2(fds[1], 1);
 		close(fds[0]);

xargs.c

@@ -164,15 +164,13 @@ waitchld(void)
 static void
 spawn(void)
 {
-	pid_t pid;
 	int savederrno;
 
-	pid = fork();
-	if (pid < 0) {
+	switch (fork()) {
+	case -1:
 		weprintf("fork:");
 		_exit(1);
-	}
-	if (pid == 0) {
+	case 0:
 		execvp(*cmd, cmd);
 		savederrno = errno;
 		weprintf("execvp %s:", *cmd);