sd-login: add C API to query primary session of a user

3 files changed, 48 insertions, 8 deletions

diff --git a/src/libsystemd/libsystemd.sym.m4 b/src/libsystemd/libsystemd.sym.m4
index 7545ae4dc1..61952d7621 100644
--- a/src/libsystemd/libsystemd.sym.m4
+++ b/src/libsystemd/libsystemd.sym.m4
@@ -135,6 +135,11 @@ global:
         sd_peer_get_user_unit;
         sd_peer_get_machine_name;
         sd_peer_get_slice;
+} LIBSYSTEMD_209;
+
+LIBSYSTEMD_213 {
+global:
+        sd_uid_get_display;
 
 m4_ifdef(`ENABLE_KDBUS',
         /* sd-bus */
@@ -427,4 +432,4 @@ m4_ifdef(`ENABLE_KDBUS',
         sd_resolve_query_set_userdata;
         sd_resolve_query_get_resolve;
 )
-} LIBSYSTEMD_209;
+} LIBSYSTEMD_211;
diff --git a/src/libsystemd/sd-login/sd-login.c b/src/libsystemd/sd-login/sd-login.c
index e7eea19580..375a5388aa 100644
--- a/src/libsystemd/sd-login/sd-login.c
+++ b/src/libsystemd/sd-login/sd-login.c
@@ -165,6 +165,15 @@ _public_ int sd_peer_get_slice(int fd, char **slice) {
         return cg_pid_get_slice(ucred.pid, slice);
 }
 
+static int file_of_uid(uid_t uid, char **p) {
+        assert(p);
+
+        if (asprintf(p, "/run/systemd/users/" UID_FMT, uid) < 0)
+                return -ENOMEM;
+
+        return 0;
+}
+
 _public_ int sd_uid_get_state(uid_t uid, char**state) {
         _cleanup_free_ char *p = NULL;
         char *s = NULL;
@@ -172,8 +181,9 @@ _public_ int sd_uid_get_state(uid_t uid, char**state) {
 
         assert_return(state, -EINVAL);
 
-        if (asprintf(&p, "/run/systemd/users/"UID_FMT, uid) < 0)
-                return -ENOMEM;
+        r = file_of_uid(uid, &p);
+        if (r < 0)
+                return r;
 
         r = parse_env_file(p, NEWLINE, "STATE", &s, NULL);
         if (r == -ENOENT) {
@@ -192,6 +202,29 @@ _public_ int sd_uid_get_state(uid_t uid, char**state) {
         return 0;
 }
 
+_public_ int sd_uid_get_display(uid_t uid, char **session) {
+        _cleanup_free_ char *p = NULL, *s = NULL;
+        int r;
+
+        assert_return(session, -EINVAL);
+
+        r = file_of_uid(uid, &p);
+        if (r < 0)
+                return r;
+
+        r = parse_env_file(p, NEWLINE, "DISPLAY", &s, NULL);
+        if (r < 0)
+                return r;
+
+        if (isempty(s))
+                return -ENOENT;
+
+        *session = s;
+        s = NULL;
+
+        return 0;
+}
+
 _public_ int sd_uid_is_on_seat(uid_t uid, int require_active, const char *seat) {
         char *w, *state;
         _cleanup_free_ char *t = NULL, *s = NULL, *p = NULL;
@@ -231,8 +264,9 @@ static int uid_get_array(uid_t uid, const char *variable, char ***array) {
         char **a;
         int r;
 
-        if (asprintf(&p, "/run/systemd/users/"UID_FMT, uid) < 0)
-                return -ENOMEM;
+        r = file_of_uid(uid, &p);
+        if (r < 0)
+                return r;
 
         r = parse_env_file(p, NEWLINE,
                            variable, &s,
@@ -362,7 +396,6 @@ _public_ int sd_session_get_state(const char *session, char **state) {
                 return r;
 
         r = parse_env_file(p, NEWLINE, "STATE", &s, NULL);
-
         if (r < 0)
                 return r;
         else if (!s)
@@ -405,7 +438,6 @@ static int session_get_string(const char *session, const char *field, char **val
                 return r;
 
         r = parse_env_file(p, NEWLINE, field, &s, NULL);
-
         if (r < 0)
                 return r;
 
diff --git a/src/systemd/sd-login.h b/src/systemd/sd-login.h
index 776733ad1d..dad459a7e8 100644
--- a/src/systemd/sd-login.h
+++ b/src/systemd/sd-login.h
@@ -103,7 +103,10 @@ int sd_peer_get_machine_name(int fd, char **machine);
 int sd_peer_get_slice(int fd, char **slice);
 
 /* Get state from UID. Possible states: offline, lingering, online, active, closing */
-int sd_uid_get_state(uid_t uid, char**state);
+int sd_uid_get_state(uid_t uid, char **state);
+
+/* Return primary session of user, if there is any */
+int sd_uid_get_display(uid_t uid, char **session);
 
 /* Return 1 if UID has session on seat. If require_active is true, this will
  * look for active sessions only. */