system_data_types(7) - Linux manual page (original) (raw)

systemdatatypes(7) Miscellaneous Information Manual_systemdatatypes_(7)

NAME top

   system_data_types - overview of system data types

DESCRIPTION top

   _siginfot_
          _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;   /* Memory location which caused fault */
              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)](../man2/sigaction.2.html).

          _Conforming to_: POSIX.1-2001 and later.

          _See also_: [pidfd_send_signal(2)](../man2/pidfd%5Fsend%5Fsignal.2.html), [rt_sigqueueinfo(2)](../man2/rt%5Fsigqueueinfo.2.html),
          [sigaction(2)](../man2/sigaction.2.html), [sigwaitinfo(2)](../man2/sigwaitinfo.2.html), [psiginfo(3)](../man3/psiginfo.3.html)

   _sigsett_
          _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)](../man2/epoll%5Fpwait.2.html), [ppoll(2)](../man2/ppoll.2.html), [pselect(2)](../man2/pselect.2.html),
          [sigaction(2)](../man2/sigaction.2.html), [signalfd(2)](../man2/signalfd.2.html), [sigpending(2)](../man2/sigpending.2.html), [sigprocmask(2)](../man2/sigprocmask.2.html),
          [sigsuspend(2)](../man2/sigsuspend.2.html), [sigwaitinfo(2)](../man2/sigwaitinfo.2.html), [signal(7)](../man7/signal.7.html)

NOTES top

   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)](../man3/printf.3.html) and the [scanf(3)](../man3/scanf.3.html)
   families of functions.  To print a value of an integer type that
   doesn't have a length modifier, it should be converted to _intmaxt_
   or _uintmaxt_ 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 _intmaxt_ or _uintmaxt_ 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 top

   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 _intmaxt_, 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);
   }

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Linux man-pages 6.10 2024-06-15 systemdatatypes(7)