SEM_GETVALUE(3)            POSIX Programmer's Manual           SEM_GETVALUE(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NNAAMMEE
       sem_getvalue -- get the value of a semaphore

SSYYNNOOPPSSIISS
       #include <semaphore.h>

       int sem_getvalue(sem_t *restrict _s_e_m, int *restrict _s_v_a_l);

DDEESSCCRRIIPPTTIIOONN
       The _s_e_m___g_e_t_v_a_l_u_e() function shall update the location referenced by the
       _s_v_a_l argument to have the value of the semaphore referenced by _s_e_m
       without affecting the state of the semaphore. The updated value
       represents an actual semaphore value that occurred at some unspecified
       time during the call, but it need not be the actual value of the
       semaphore when it is returned to the calling process.

       If _s_e_m is locked, then the object to which _s_v_a_l points shall either be
       set to zero or to a negative number whose absolute value represents the
       number of processes waiting for the semaphore at some unspecified time
       during the call.

RREETTUURRNN VVAALLUUEE
       Upon successful completion, the _s_e_m___g_e_t_v_a_l_u_e() function shall return a
       value of zero. Otherwise, it shall return a value of -1 and set _e_r_r_n_o
       to indicate the error.

EERRRROORRSS
       The _s_e_m___g_e_t_v_a_l_u_e() function may fail if:

       EEIINNVVAALL The _s_e_m argument does not refer to a valid semaphore.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       None.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _s_e_m_c_t_l(), _s_e_m_g_e_t(), _s_e_m_o_p(), _s_e_m___p_o_s_t(), _s_e_m___t_i_m_e_d_w_a_i_t(), _s_e_m___t_r_y_w_a_i_t()

       The Base Definitions volume of POSIX.1-2017, <<sseemmaapphhoorree..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                      SEM_GETVALUE(3)
