NAME

       system_data_types - overview of system data types

DESCRIPTION

       sigevent
              Include: <signal.h>.  Alternatively, <aio.h>, <mqueue.h>, or <time.h>.

              struct sigevent {
                  int             sigev_notify; /* Notification type */
                  int             sigev_signo;  /* Signal number */
                  union sigval    sigev_value;  /* Signal value */
                  void          (*sigev_notify_function)(union sigval);
                                                /* Notification function */
                  pthread_attr_t *sigev_notify_attributes;
                                                /* Notification attributes */
              };

              For further details about this type, see sigevent(7).

              Versions: <aio.h> and <time.h> define sigevent since POSIX.1-2008.

              Conforming to: POSIX.1-2001 and later.

              See also: timer_create(2), getaddrinfo_a(3), lio_listio(3), mq_notify(3)

              See also the aiocb structure in this page.

       siginfo_t
              Include: <signal.h>.  Alternatively, <sys/wait.h>.

              typedef struct {
                  int      si_signo;  /* Signal number */
                  int      si_code;   /* Signal code */
                  pid_t    si_pid;    /* Sending process ID */
                  uid_t    si_uid;    /* Real user ID of sending process */
                  void    *si_addr;   /* Address of faulting instruction */
                  int      si_status; /* Exit value or signal */
                  union sigval si_value;  /* Signal value */
              } siginfo_t;

              Information  associated  with  a  signal.   For  further  details on this structure
              (including additional, Linux-specific fields), see sigaction(2).

              Conforming to: POSIX.1-2001 and later.

              See also: pidfd_send_signal(2), rt_sigqueueinfo(2),  sigaction(2),  sigwaitinfo(2),
              psiginfo(3)

       sigset_t
              Include: <signal.h>.  Alternatively, <spawn.h>, or <sys/select.h>.

              This is a type that represents a set of signals.  According to POSIX, this shall be
              an integer or structure type.

              Conforming to: POSIX.1-2001 and later.

              See  also:  epoll_pwait(2),  ppoll(2),   pselect(2),   sigaction(2),   signalfd(2),
              sigpending(2), sigprocmask(2), sigsuspend(2), sigwaitinfo(2), signal(7)

       sigval
              Include: <signal.h>.

              union sigval {
                  int     sigval_int; /* Integer value */
                  void   *sigval_ptr; /* Pointer value */
              };

              Data passed with a signal.

              Conforming to: POSIX.1-2001 and later.

              See also: pthread_sigqueue(3), sigqueue(3), sigevent(7)

              See also the sigevent structure and the siginfo_t type in this page.

NOTES

       The structures described in this manual page shall contain, at least, the members shown in
       their definition, in no particular order.

       Most of the integer types described  in  this  page  don't  have  a  corresponding  length
       modifier for the printf(3) and the scanf(3) families of functions.  To print a value of an
       integer type that doesn't have a length modifier, it should be converted  to  intmax_t  or
       uintmax_t  by  an  explicit cast.  To scan into a variable of an integer type that doesn't
       have a length modifier, an intermediate temporary variable of type intmax_t  or  uintmax_t
       should be used.  When copying from the temporary variable to the destination variable, the
       value could overflow.  If the type has upper and lower limits, the user should check  that
       the  value  is  within those limits, before actually copying the value.  The example below
       shows how these conversions should be done.

   Conventions used in this page
       In "Conforming to" we only concern ourselves with  C99  and  later  and  POSIX.1-2001  and
       later.   Some types may be specified in earlier versions of one of these standards, but in
       the interests of simplicity we omit details from earlier standards.

       In "Include", we first note the "primary" header(s) that  define  the  type  according  to
       either the C or POSIX.1 standards.  Under "Alternatively", we note additional headers that
       the standards specify shall define the type.

EXAMPLES

       The program shown below scans from a string and prints a value stored in a variable of  an
       integer type that doesn't have a length modifier.  The appropriate conversions from and to
       intmax_t, and the appropriate range checks, are used as explained  in  the  notes  section
       above.

       #include <stdint.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <sys/types.h>

       int
       main (void)
       {
           static const char *const str = "500000 us in half a second";
           suseconds_t us;
           intmax_t    tmp;

           /* Scan the number from the string into the temporary variable. */

           sscanf(str, "%jd", &tmp);

           /* Check that the value is within the valid range of suseconds_t. */

           if (tmp < -1 || tmp > 1000000) {
               fprintf(stderr, "Scanned value outside valid range!\n");
               exit(EXIT_FAILURE);
           }

           /* Copy the value to the suseconds_t variable 'us'. */

           us = tmp;

           /* Even though suseconds_t can hold the value -1, this isn't
              a sensible number of microseconds. */

           if (us < 0) {
               fprintf(stderr, "Scanned value shouldn't be negative!\n");
               exit(EXIT_FAILURE);
           }

           /* Print the value. */

           printf("There are %jd microseconds in half a second.\n",
                   (intmax_t) us);

           exit(EXIT_SUCCESS);
       }

SEE ALSO

       feature_test_macros(7), standards(7)