hostname: Add ability to set node name

1 files changed, 59 insertions, 3 deletions

diff --git a/hostname/hostname.c b/hostname/hostname.c
index 3dc1224..d19e4b8 100644
--- a/hostname/hostname.c
+++ b/hostname/hostname.c
@@ -18,6 +18,18 @@
 #include <sys/socket.h>
 #include <netdb.h>
 
+/* open, read, close */
+#include <sys/stat.h>
+#include <fcntl.h>
+
+int sethostname(const char *value,
+#ifdef __linux__
+	size_t
+#else
+	int
+#endif
+	namelen);
+
 int do_print_nodename(bool verbose, bool domain, bool fqdn, bool address, bool shorten)
 {
 	long hostname = sysconf(_SC_HOST_NAME_MAX);
@@ -113,9 +125,53 @@ int do_print_nodename(bool verbose, bool domain, bool fqdn, bool address, bool s
 
 int do_set_nodename(bool file, const char *value)
 {
-	fprintf(stderr, "setting nodenamet to %s %s not yet supported\n",
-		(file ? "contents of file" : "literal string"), value);
-	return 1;
+	size_t len;
+
+	if(file)
+	{
+		/* This is insane.  There is no validation whatsoever.
+		 * However, strace on net-tools hostname(1) shows this to be
+		 * the exact algorithm used, so... */
+		char buf[1024];
+		int fildes = open(value, O_RDONLY);
+		ssize_t result = 0;
+
+		if(fildes == -1)
+		{
+			perror("open");
+			return EXIT_FAILURE;
+		}
+
+		while(true)
+		{
+			char *curr = buf;
+			result = read(fildes, buf, sizeof buf);
+			switch(result)
+			{
+			case -1:
+				perror("read");
+				close(fildes);
+				return EXIT_FAILURE;
+			case 0:
+				close(fildes);
+				return EXIT_SUCCESS;
+			}
+			do
+			{
+				len = result;
+				char *pos = strchr(curr, '\n');
+				if(pos)
+				{
+					len = pos - curr;
+				}
+				sethostname(curr, (len > 63) ? 63 : len);
+			} while((curr = strchr(curr, '\n')));
+		}
+	}
+
+	len = strlen(value);
+	sethostname(value, len);
+	return EXIT_SUCCESS;
 }
 
 void usage()