libbb: split update_utmp from login/getty in preparation to use it for telnetd

function                                             old     new   delta
update_utent                                           -     339    +339
login_main                                          1498    1128    -370
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/1 up/down: 339/-370)          Total: -31 bytes

function                                             old     new   delta
update_utmp                                          246     337     +91
login_main                                          1128    1140     +12
getty_main                                          1908    1918     +10
...
update_utent                                         339       -    -339
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 5/6 up/down: 119/-368)         Total: -249 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/libbb.h b/include/libbb.h
index e674e4aea..ea61701b7 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -796,6 +796,12 @@ void die_if_bad_username(const char* name) FAST_FUNC;
 #define die_if_bad_username(name) ((void)(name))
 #endif
 
+#if ENABLE_FEATURE_UTMP
+void FAST_FUNC update_utmp(int new_type, const char *short_tty, const char *username, const char *opt_host);
+#else
+# define update_utmp(new_type, short_tty, username, opt_host) ((void)0)
+#endif
+
 int execable_file(const char *name) FAST_FUNC;
 char *find_execable(const char *filename, char **PATHp) FAST_FUNC;
 int exists_execable(const char *filename) FAST_FUNC;