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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |NOTES |HISTORY |SEE ALSO |COLOPHON | |
SD_UID_GET_STATE(3) sd_uid_get_stateSD_UID_GET_STATE(3)sd_uid_get_state, sd_uid_is_on_seat, sd_uid_get_sessions, sd_uid_get_seats, sd_uid_get_display, sd_uid_get_login_time - Determine login state of a specific Unix user ID
#include <systemd/sd-login.h>int sd_uid_get_state(uid_tuid, char **state);int sd_uid_is_on_seat(uid_tuid, intrequire_active,const char *seat);int sd_uid_get_sessions(uid_tuid, intrequire_active,char ***sessions);int sd_uid_get_seats(uid_tuid, intrequire_active,char ***seats);int sd_uid_get_display(uid_tuid, char **session);int sd_uid_get_login_time(uid_tuid, uint64_t *usec);
sd_uid_get_state()may be used to determine the login state of a specific Unix user identifier. The following states are currently known: "offline" (user not logged in at all), "lingering" (user not logged in, but some user services running), "online" (user logged in, but not active, i.e. has no session in the foreground), "active" (user logged in, and has at least one active session, i.e. one session in the foreground), "closing" (user not logged in, and not lingering, but some processes are still around). In the future additional states might be defined, client code should be written to be robust in regards to additional state strings being returned. The returned string needs to be freed with the libcfree(3) call after use.sd_uid_is_on_seat()may be used to determine whether a specific user is logged in or active on a specific seat. Accepts a Unix user identifier and a seat identifier string as parameters. Therequire_active parameter is a boolean value. If non-zero (true), this function will test if the user is active (i.e. has a session that is in the foreground and accepting user input) on the specified seat, otherwise (false) only if the user is logged in (and possibly inactive) on the specified seat.sd_uid_get_sessions()may be used to determine the current sessions of the specified user. Accepts a Unix user identifier as parameter. Therequire_active parameter controls whether the returned list shall consist of only those sessions where the user is currently active (> 0), where the user is currently online but possibly inactive (= 0), or logged in but possibly closing the session (< 0). The call returns aNULLterminated string array of session identifiers insessions which needs to be freed by the caller with the libcfree(3) call after use, including all the strings referenced. If the string array parameter is passed asNULL, the array will not be filled in, but the return code still indicates the number of current sessions. Note that instead of an empty arrayNULLmay be returned and should be considered equivalent to an empty array. Similarly,sd_uid_get_seats()may be used to determine the list of seats on which the user currently has sessions. Similar semantics apply, however note that the user may have multiple sessions on the same seat as well as sessions with no attached seat and hence the number of entries in the returned array may differ from the one returned bysd_uid_get_sessions().sd_uid_get_display()returns the name of the "primary" session of a user. If the user has graphical sessions, it will be the oldest graphical session. Otherwise, it will be the oldest open session.sd_uid_get_login_time()may be used to determine the time the user's service manager has been invoked, which is the time when the user's first active session, since which they stayed logged in continuously, began. Theusec is in microseconds since the epoch (CLOCK_REALTIME). This call will fail with-ENXIOif the user is not currently logged in.
On success,sd_uid_get_state()andsd_uid_get_login_time()returns 0 or a positive integer. If the test succeeds,sd_uid_is_on_seat() returns a positive integer; if it fails, 0.sd_uid_get_sessions() andsd_uid_get_seats()return the number of entries in the returned arrays.sd_uid_get_display()returns a non-negative code on success. On failure, these calls return a negative errno-style error code.Errors Returned errors may indicate the following problems:-ENODATA The given field is not specified for the described user.-ENXIO The specified seat is unknown.-EINVAL An input parameter was invalid (out of range, orNULL, where that is not accepted). This is also returned if the passed user ID is0xFFFFor0xFFFFFFFF, which are undefined on Linux.-ENOMEM Memory allocation failed.
Functions described here are available as a shared library, which can be compiled against and linked to with thelibsystemd pkg-config(1) file. The code described here usesgetenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not callsetenv(3) from a parallel thread. It is recommended to only do calls tosetenv()from an early phase of the program when no other threads have been started.
sd_uid_get_display()was added in version 213.sd_uid_get_login_time()was added in version 254.
systemd(1),sd-login(3),sd_pid_get_owner_uid(3)
This page is part of thesystemd (systemd system and service manager) project. Information about the project can be found at ⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug report for this manual page, see ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This page was obtained from the project's upstream Git repository ⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-08-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgsystemd 258~rc2SD_UID_GET_STATE(3)Pages that refer to this page:sd-login(3), org.freedesktop.login1(5), systemd.directives(7), systemd.index(7)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |