SD_SESSION_IS_ACTIVE(3)

📦

version 261.3 · 17 versions

💅 SD_SESSION_IS_ACTIVE(3) — the session-info manual, bestie edition 💅

okay so this is the SD_SESSION_IS_ACTIVE(3) page, and it’s literally a whole squad of libsystemd calls that tell you stuff about a specific session. no cap: the facts below are the whole manual, just with way more sparkle. ✨

🌸 NAME 🌸

meet the lineup — all of these are here to determine state of a specific session:

sd_session_is_active
sd_session_is_remote
sd_session_get_state
sd_session_get_uid
sd_session_get_username
sd_session_get_seat
sd_session_get_start_time
sd_session_get_service
sd_session_get_type
sd_session_get_class
sd_session_get_desktop
sd_session_get_display
sd_session_get_tty
sd_session_get_vt
sd_session_get_remote_host
sd_session_get_remote_user
sd_session_get_leader
sd_session_get_extra_device_access

periodt. that’s the whole friend group. 🫶

✨ SYNOPSIS ✨

grab the header like this, bestie:

       #include <systemd/sd-login.h>

       int sd_session_is_active(const char *session);

       int sd_session_is_remote(const char *session);

       int sd_session_get_state(const char *session, char **state);

       int sd_session_get_uid(const char *session, uid_t *uid);

       int sd_session_get_username(const char *session, char **username);

       int sd_session_get_seat(const char *session, char **seat);

       int sd_session_get_start_time(const char *session, uint64_t *usec);

       int sd_session_get_service(const char *session, char **service);

       int sd_session_get_type(const char *session, char **type);

       int sd_session_get_class(const char *session, char **class);

       int sd_session_get_desktop(const char *session, char **desktop);

       int sd_session_get_display(const char *session, char **display);

       int sd_session_get_leader(const char *session, pid_t *leader);

       int sd_session_get_remote_host(const char *session, char **remote_host);

       int sd_session_get_remote_user(const char *session, char **remote_user);

       int sd_session_get_tty(const char *session, char **tty);

       int sd_session_get_vt(const char *session, unsigned int *vt);

       int sd_session_get_extra_device_access(const char *session,
                                              char ***ret_ids);

🦋 DESCRIPTION 🦋

each function is its own little main character. here’s the tea on every single one:

sd_session_is_active() — use this to figure out whether the session identified by the specified session identifier is currently active (i.e. currently in the foreground and available for user input) or not.
sd_session_is_remote() — use this to figure out whether the session identified by the specified session identifier is a remote session (i.e. its remote host is known) or not.
sd_session_get_state() — use this to figure out the state of the session identified by the specified session identifier. these states are currently known: "online" (session logged in, but session not active, i.e. not in the foreground), "active" (session logged in and active, i.e. in the foreground), "closing" (session nominally logged out, but some processes belonging to it are still around). in the future additional states might be defined, so client code should be written to be robust in regards to additional state strings being returned. this function is a more generic version of sd_session_is_active(). the returned string needs to be freed with the libc free(3) call after use. 🧚
sd_session_get_uid() — use this to figure out the user identifier of the Unix user the session identified by the specified session identifier belongs to.
sd_session_get_username() — use this to figure out the name of the Unix user the session identified by the specified session identifier belongs to. the returned string needs to be freed with the libc free(3) call after use.
sd_session_get_seat() — use this to figure out the seat identifier of the seat the session identified by the specified session identifier belongs to. note that not all sessions are attached to a seat — this call will fail (returning -ENODATA) for them. the returned string needs to be freed with the libc free(3) call after use. 🎀
sd_session_get_start_time() — use this to figure out the start time that belongs to the session identified by the specified session identifier. the usec is in microseconds since the epoch (CLOCK_REALTIME).
sd_session_get_service() — use this to figure out the name of the service (as passed during PAM session setup) that registered the session identified by the specified session identifier. the returned string needs to be freed with the libc free(3) call after use.
sd_session_get_type() — use this to figure out the type of the session identified by the specified session identifier. the returned string is one of "x11", "wayland", "tty", "mir" or "unspecified" and needs to be freed with the libc free(3) call after use.
sd_session_get_class() — use this to figure out the class of the session identified by the specified session identifier. the returned string is one of "user", "user-early", "user-light", "user-early-light", "user-incomplete", "greeter", "lock-screen", "background", "background-light", "manager" or "manager-early" and needs to be freed with the libc free(3) call after use. 💅
sd_session_get_desktop() — use this to figure out the brand of the desktop running on the session identified by the specified session identifier. this field can be set freely by desktop environments and does not follow any special formatting. however, desktops are strongly recommended to use the same identifiers and capitalization as for $XDG_CURRENT_DESKTOP, as defined by the Desktop Entry Specification[1]. the returned string needs to be freed with the libc free(3) call after use.
sd_session_get_display() — use this to figure out the X11 display of the session identified by the specified session identifier. the returned string needs to be freed with the libc free(3) call after use.
sd_session_get_leader() — use this to figure out the PID of the leader of the session identified by the specified session identifier.
sd_session_get_remote_host() — use this to figure out the remote hostname of the session identified by the specified session identifier. the returned string needs to be freed with the libc free(3) call after use.
sd_session_get_remote_user() — use this to figure out the remote username of the session identified by the specified session identifier. the returned string needs to be freed with the libc free(3) call after use. note that this value is rarely known to the system, and even then should not be relied on. 🙈
sd_session_get_tty() — use this to figure out the TTY device of the session identified by the specified session identifier. the returned string needs to be freed with the libc free(3) call after use.
sd_session_get_vt() — use this to figure out the VT number of the session identified by the specified session identifier. this function will return an error if the seat does not support VTs.
sd_session_get_extra_device_access() — use this to figure out which additional hardware devices the session is granted access to. for every "ID" in the list, the session is granted access to all devices tagged with "xaccess-ID" in udev. 🔥

and one more lil detail that applies to all of them: if the session parameter of any of these functions is passed as NULL, the operation is executed for the session the calling process is a member of, if there is any.

🔥 RETURN VALUE 🔥

if the test succeeds, sd_session_is_active() and sd_session_is_remote() return a positive integer; if it fails, 0.

on success, these calls return 0 or a positive integer: sd_session_get_state(), sd_session_get_uid(), sd_session_get_username(), sd_session_get_seat(), sd_session_get_service(), sd_session_get_type(), sd_session_get_class(), sd_session_get_display(), sd_session_get_leader(), sd_session_get_remote_user(), sd_session_get_remote_host(), sd_session_get_tty(), and sd_session_get_extra_device_access().

on failure, these calls return a negative errno-style error code.

😭 Errors 😭

returned errors may indicate the following problems:

-ENXIO — the specified session does not exist.
-ENODATA — the given field is not specified for the described session.
-EINVAL — an input parameter was invalid (out of range, or NULL, where that is not accepted).
-ENOMEM — memory allocation failed.

📝 NOTES 📝

the functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config(1) file.

⚠️ thread-safety tea, bestie: the code described here uses getenv(3), which is declared to be not multi-thread-safe. this means that the code calling the functions described here must not call setenv(3) from a parallel thread. it is recommended to only do calls to setenv() from an early phase of the program when no other threads have been started. 🫶

👑 HISTORY 👑

sd_session_get_state() was added in version 186.
sd_session_get_tty() was added in version 198.
sd_session_get_vt() was added in version 207.
sd_session_is_remote(), sd_session_get_remote_host(), and sd_session_get_remote_user() were added in version 209.
sd_session_get_desktop() was added in version 217.
sd_session_get_username(), sd_session_get_start_time(), and sd_session_get_leader() were added in version 254.
sd_session_get_extra_device_access() was added in version 260.

🌈 SEE ALSO 🌈

🎀 NOTES (the footnote one) 🎀

Desktop Entry Specification — https://standards.freedesktop.org/desktop-entry-spec/latest/

okay bestie, that’s the whole page. this is systemd 261.3’s SD_SESSION_IS_ACTIVE(3) manual — the footer didn’t hand me a date, so I’m not out here inventing one. now go check those sessions, slay 💅✨

📦 where this page comes from

ubuntu stonking: libsystemd-dev 261.3-0ubuntu3 · LGPL-2.1-or-later
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-06: a language model's rewrite of the original, under its terms