NAME
sd_login_monitor_new, sd_login_monitor_unref, sd_login_monitor_unrefp, sd_login_monitor_flush, sd_login_monitor_get_fd, sd_login_monitor_get_events, sd_login_monitor_get_timeout, sd_login_monitor - Monitor login sessions, seats, users and virtual machines/containersSYNOPSIS
#include <systemd/sd-login.h>
int
sd_login_monitor_new(const char *category,
sd_login_monitor **ret);
sd_login_monitor
*sd_login_monitor_unref(sd_login_monitor *m);
void
sd_login_monitor_unrefp(sd_login_monitor **m);
int
sd_login_monitor_flush(sd_login_monitor *m);
int
sd_login_monitor_get_fd(sd_login_monitor *m);
int
sd_login_monitor_get_events(sd_login_monitor *m);
int
sd_login_monitor_get_timeout(sd_login_monitor *m,
uint64_t *timeout_usec);
DESCRIPTION
sd_login_monitor_new() may be used to monitor login sessions, users, seats, and virtual machines/containers. Via a monitor object a file descriptor can be integrated into an application defined event loop which is woken up each time a user logs in, logs out or a seat is added or removed, or a session, user, seat or virtual machine/container changes state otherwise. The first parameter takes a string which can be "seat" (to get only notifications about seats being added, removed or changed), "session" (to get only notifications about sessions being created or removed or changed), "uid" (to get only notifications when a user changes state in respect to logins) or "machine" (to get only notifications when a virtual machine or container is started or stopped). If notifications shall be generated in all these conditions, NULL may be passed. Note that in the future additional categories may be defined. The second parameter returns a monitor object and needs to be freed with the sd_login_monitor_unref() call after use. sd_login_monitor_unref() may be used to destroy a monitor object. Note that this will invalidate any file descriptor returned by sd_login_monitor_get_fd(). sd_login_monitor_unrefp() is similar to sd_login_monitor_unref() but takes a pointer to a pointer to an sd_login_monitor object. This call is useful in conjunction with GCC's and LLVM's Clean-up Variable Attribute[1]. Note that this function is defined as inline function. Use a declaration like the following, in order to allocate a login monitor object that is freed automatically as the code block is left:{ __attribute__((cleanup(sd_login_monitor_unrefp))) sd_login_monitor *m = NULL; int r; ... r = sd_login_monitor_new(NULL, &m); if (r < 0) { errno = -r; fprintf(stderr, "Failed to allocate login monitor object: %m\n"); } ... }
uint64_t t; int msec; sd_login_monitor_get_timeout(m, &t); if (t == (uint64_t) -1) msec = -1; else { struct timespec ts; uint64_t n; clock_gettime(CLOCK_MONOTONIC, &ts); n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000; msec = t > n ? (int) ((t - n + 999) / 1000) : 0; }
RETURN VALUE
On success, sd_login_monitor_new(), sd_login_monitor_flush() and sd_login_monitor_get_timeout() return 0 or a positive integer. On success, sd_login_monitor_get_fd() returns a Unix file descriptor. On success, sd_login_monitor_get_events() returns a combination of POLLIN, POLLOUT and suchlike. On failure, these calls return a negative errno-style error code. sd_login_monitor_unref() always returns NULL.Errors
Returned errors may indicate the following problems: -EINVALAn input parameter was invalid (out of range,
or NULL, where that is not accepted). The specified category to watch
is not known.
-ENOMEM
Memory allocation failed.
NOTES
These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd pkg-config(1) file.SEE ALSO
systemd(1), sd-login(3), sd_get_seats(3), poll(2), clock_gettime(2)NOTES
- 1.
- Clean-up Variable Attribute
systemd 252 |