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Top Forums Programming String array iteration causing segfault Post 302847743 by Corona688 on Tuesday 27th of August 2013 04:32:03 PM
Old 08-27-2013
You made it an array of arrays, guaranteeing it will never be NULL. array[j] just calculates array + (j*50), which isn't going to be zero.

If you want to store a null pointer, you'll have to store pointers. Then you get address stored at (base_address + j) which is quite capable of being NULL.

char *strings[]={
                NULL };

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SD_SEAT_GET_ACTIVE(3)						sd_seat_get_active					     SD_SEAT_GET_ACTIVE(3)

sd_seat_get_active, sd_seat_get_sessions, sd_seat_can_multi_session - Determine state of a specific seat SYNOPSIS
#include <systemd/sd-login.h> int sd_seat_get_active(const char* seat, char** session, uid_t* uid); int sd_seat_get_sessions(const char* seat, char*** sessions, uid_t** uid, unsigned* n_uids); int sd_seat_can_multi_session(const char* seat); DESCRIPTION
sd_seat_get_active() may be used to determine which session is currently active on a seat, if there is any. Returns the session identifier and the user identifier of the Unix user the session is belonging to. Either the session or the user identifier parameter can be be passed NULL, in case only one of the parameters shall be queried. The returned string needs to be freed with the libc free(3) call after use. sd_seat_get_sessions() may be used to determine all sessions on the specified seat. Returns two arrays, one (NULL terminated) with the session identifiers of the sessions and one with the user identifiers of the Unix users the sessions belong to. An additional parameter may be used to return the number of entries in the latter array. The two arrays and the latter parameter may be passed as NULL in case these values need not to be determined. The arrays and the strings referenced by them need to be freed with the libc free(3) call after use. Note that instead of an empty array NULL may be returned and should be considered equivalent to an empty array. sd_seat_can_multi_session() may be used to determine whether a specific seat is capable of multi-session, i.e. allows multiple login sessions in parallel (whith only one being active at a time). If the seat parameter of any of these functions is passed as NULL the operation is executed for the seat of the session of the calling process, if there is any. RETURN VALUE
On success sd_seat_get_active() return return 0 or a positive integer. On success sd_seat_get_sessions() returns the number of entries in the session identifier array. If the test succeeds sd_seat_can_multi_session returns a positive integer, if it fails 0. On failure, these calls return a negative errno-style error code. NOTES
The sd_seat_get_active(), sd_seat_get_sessions(), and sd_seat_can_multi_session() interfaces are available as shared library, which can be compiled and linked to with the libsystemd-login pkg-config(1) file. SEE ALSO
systemd(1), sd-login(7), sd_session_get_seat(3) AUTHOR
Lennart Poettering <> Developer systemd 10/07/2013 SD_SEAT_GET_ACTIVE(3)

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