Fix hostname printing.

ssh doesn't set HOSTNAME in env, that has to be determined separately.
What indicates a ssh session are some SSH_* env vars.

Makefile

@@ -13,7 +13,7 @@ bindir = $(PREFIX)/bin
 
 all: ep
 
-ep: ep.c out.c path.c git.c lang.c $(LANGUAGE)
+ep: ep.c out.c path.c git.c lang.c ssh.c $(LANGUAGE)
 
 install: ep
 	install -m755 $< $(bindir)/ep

ep.c

@@ -71,13 +71,9 @@ int main(int argc, char **argv)
 		p("[chroot] ");
 
 	const char *home = getenv("HOME");
-	const char *hostname = getenv("HOSTNAME");
 
 	/* show we are on a different machine */
-	if (hostname) {
-		p(hostname);
-		p(" ");
-	}
+	print_ssh();
 
 	print_pwd(home);
 

ep.h

@@ -35,4 +35,7 @@ void print_git(void);
 void *lang_thread(void *);
 void print_lang(uint64_t);
 
+/* from ssh.c */
+void print_ssh(void);
+
 #endif

ssh.c

@@ -0,0 +1,21 @@
+#include <stdlib.h>
+#include <sys/utsname.h>
+
+#include "ep.h"
+
+void print_ssh(void)
+{
+	/* expect ssh to have set these variables - we don't need to prompt if not using a tty */
+	const char *sshcon = getenv("SSH_CONNECTION"), *sshtty = getenv("SSH_TTY");
+
+	if (sshcon && *sshcon && sshtty && *sshtty) {
+		struct utsname u;
+		/* don't print anything if uname fails or nodename is empty */
+		if (uname(&u) || !u.nodename[0])
+			return;
+
+		p("(");
+		p(u.nodename);
+		p(") ");
+	}
+}