system_data_types(7) — Linux manual page


system...a_types(7) Miscellaneous Information Manual system...a_types(7)

NAME         top

       system_data_types - overview of system data types

DESCRIPTION         top

              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).

              Conforming to: POSIX.1-2001 and later.

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

              Include: <signal.h>.  Alternatively, <spawn.h>, or

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

              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)

NOTES         top

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

       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         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
       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>

       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");

           /* 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");

           /* Print the value. */

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


SEE ALSO         top

       feature_test_macros(7), standards(7)

COLOPHON         top

       This page is part of the man-pages (Linux kernel and C library
       user-space interface documentation) project.  Information about
       the project can be found at 
       ⟨⟩.  If you have a bug report
       for this manual page, see
       This page was obtained from the tarball man-pages-6.9.1.tar.gz
       fetched from
       ⟨⟩ on
       2024-06-26.  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-
       to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not
       part of the original manual page), send a mail to

Linux man-pages 6.9.1          2024-06-15            system...a_types(7)

Pages that refer to this page: intro(2)intro(3)sigevent(3type)credentials(7)feature_test_macros(7)standards(7)