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NAME

       system_data_types - overview of system data types

DESCRIPTION

       aiocb
              Include: <aio.h>.

              struct aiocb {
                  int             aio_fildes;    /* File descriptor */
                  off_t           aio_offset;    /* File offset */
                  volatile void  *aio_buf;       /* Location of buffer */
                  size_t          aio_nbytes;    /* Length of transfer */
                  int             aio_reqprio;   /* Request priority offset */
                  struct sigevent aio_sigevent;  /* Signal number and value */
                  int             aio_lio_opcode;/* Operation to be performed */
              };

              For further information about this structure, see aio(7).

              Conforming to: POSIX.1-2001 and later.

              See  also:  aio_cancel(3),  aio_error(3), aio_fsync(3), aio_read(3), aio_return(3),
              aio_suspend(3), aio_write(3), lio_listio(3)

       blkcnt_t
              Include: <sys/types.h>.  Alternatively, <sys/stat.h>.

              Used for file block counts.  According to POSIX, it shall be a signed integer type.

              Conforming to: POSIX.1-2001 and later.

              See also: stat(2)

       blksize_t
              Include: <sys/types.h>.  Alternatively, <sys/stat.h>.

              Used for file block sizes.  According to POSIX, it shall be a signed integer type.

              Conforming to: POSIX.1-2001 and later.

              See also: stat(2)

       cc_t
              Include: <termios.h>.

              Used for terminal special characters.  According to POSIX, it shall be an  unsigned
              integer type.

              Conforming to: POSIX.1-2001 and later.

              See also: termios(3)

       clock_t
              Include: <time.h> or <sys/types.h>.  Alternatively, <sys/time.h>.

              Used  for  system  time  in  clock  ticks  or CLOCKS_PER_SEC (defined in <time.h>).
              According to POSIX, it shall be an integer type or a real-floating type.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: times(2), clock(3)

       clockid_t
              Include: <sys/types.h>.  Alternatively, <time.h>.

              Used for clock ID type in the clock and timer functions.  According  to  POSIX,  it
              shall be defined as an arithmetic type.

              Conforming to: POSIX.1-2001 and later.

              See  also:  clock_adjtime(2), clock_getres(2), clock_nanosleep(2), timer_create(2),
              clock_getcpuclockid(3)

       dev_t
              Include: <sys/types.h>.  Alternatively, <sys/stat.h>.

              Used for device IDs.  According to POSIX, it shall be an integer type.  For further
              details of this type, see makedev(3).

              Conforming to: POSIX.1-2001 and later.

              See also: mknod(2), stat(2)

       div_t
              Include: <stdlib.h>.

              typedef struct {
                  int quot; /* Quotient */
                  int rem;  /* Remainder */
              } div_t;

              It is the type of the value returned by the div(3) function.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: div(3)

       double_t
              Include: <math.h>.

              The  implementation's most efficient floating type at least as wide as double.  Its
              type depends on the value of the macro FLT_EVAL_METHOD (defined in <float.h>):

              0      double_t is double.

              1      double_t is double.

              2      double_t is long double.

              For other values of  FLT_EVAL_METHOD,  the  type  of  double_t  is  implementation-
              defined.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: the float_t type in this page.

       fd_set
              Include: <sys/select.h>.  Alternatively, <sys/time.h>.

              A structure type that can represent a set of file descriptors.  According to POSIX,
              the maximum number of file descriptors in an fd_set structure is the value  of  the
              macro FD_SETSIZE.

              Conforming to: POSIX.1-2001 and later.

              See also: select(2)

       fenv_t
              Include: <fenv.h>.

              This type represents the entire floating-point environment, including control modes
              and status flags; for further details, see fenv(3).

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: fenv(3)

       fexcept_t
              Include: <fenv.h>.

              This type represents the floating-point  status  flags  collectively;  for  further
              details see fenv(3).

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: fenv(3)

       FILE
              Include: <stdio.h>.  Alternatively, <wchar.h>.

              An object type used for streams.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See  also:  fclose(3),  flockfile(3),  fopen(3),  fprintf(3),  fread(3), fscanf(3),
              stdin(3), stdio(3)

       float_t
              Include: <math.h>.

              The implementation's most efficient floating type at least as wide as  float.   Its
              type depends on the value of the macro FLT_EVAL_METHOD (defined in <float.h>):

              0      float_t is float.

              1      float_t is double.

              2      float_t is long double.

              For other values of FLT_EVAL_METHOD, the type of float_t is implementation-defined.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: the double_t type in this page.

       gid_t
              Include:  <sys/types.h>.  Alternatively, <grp.h>, <pwd.h>, <signal.h>, <stropts.h>,
              <sys/ipc.h>, <sys/stat.h>, or <unistd.h>.

              A type used to hold group IDs.  According to POSIX, this shall be an integer type.

              Conforming to: POSIX.1-2001 and later.

              See also: chown(2), getgid(2), getegid(2), getgroups(2), getresgid(2), getgrnam(3),
              credentials(7)

       id_t
              Include: <sys/types.h>.  Alternatively, <sys/resource.h>.

              A  type  used  to  hold a general identifier.  According to POSIX, this shall be an
              integer type that can be used to contain a pid_t, uid_t, or gid_t.

              Conforming to: POSIX.1-2001 and later.

              See also: getpriority(2), waitid(2)

       imaxdiv_t
              Include: <inttypes.h>.

              typedef struct {
                  intmax_t    quot; /* Quotient */
                  intmax_t    rem;  /* Remainder */
              } imaxdiv_t;

              It is the type of the value returned by the imaxdiv(3) function.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: imaxdiv(3)

       intmax_t
              Include: <stdint.h>.  Alternatively, <inttypes.h>.

              A signed integer type capable of representing any value of any signed integer  type
              supported by the implementation.  According to the C language standard, it shall be
              capable of storing values in the range [INTMAX_MIN, INTMAX_MAX].

              The macro INTMAX_C() expands its argument to an integer constant of type intmax_t.

              The length modifier for intmax_t for the printf(3) and  the  scanf(3)  families  of
              functions is j; resulting commonly in %jd or %ji for printing intmax_t values.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              Bugs:  intmax_t  is  not  large  enough  to  represent  values  of type __int128 in
              implementations where __int128 is defined and long long is less than 128 bits wide.

              See also: the uintmax_t type in this page.

       intN_t
              Include: <stdint.h>.  Alternatively, <inttypes.h>.

              int8_t, int16_t, int32_t, int64_t

              A signed integer type of a fixed width  of  exactly  N  bits,  N  being  the  value
              specified  in  its  type name.  According to the C language standard, they shall be
              capable of storing values in the range [INTN_MIN, INTN_MAX], substituting N by  the
              appropriate number.

              According  to  POSIX,  int8_t,  int16_t,  and int32_t are required; int64_t is only
              required in implementations that provide integer types with width 64; and all other
              types of this form are optional.

              The length modifiers for the intN_t types for the printf(3) family of functions are
              expanded by macros  of  the  forms  PRIdN  and  PRIiN  (defined  in  <inttypes.h>);
              resulting  for  example in %"PRId64" or %"PRIi64" for printing int64_t values.  The
              length modifiers for the intN_t types for the  scanf(3)  family  of  functions  are
              expanded  by  macros  of  the  forms  SCNdN  and  SCNiN, (defined in <inttypes.h>);
              resulting for example in %"SCNd8" or %"SCNi8" for scanning int8_t values.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: the intmax_t, uintN_t, and uintmax_t types in this page.

       intptr_t
              Include: <stdint.h>.  Alternatively, <inttypes.h>.

              A signed integer type such that any valid (void *) value can be converted  to  this
              type  and  back.   According  to  the  C  language standard, it shall be capable of
              storing values in the range [INTPTR_MIN, INTPTR_MAX].

              The length modifier for intptr_t for the printf(3) family of functions is  expanded
              by  the macros PRIdPTR and PRIiPTR (defined in <inttypes.h>); resulting commonly in
              %"PRIdPTR" or %"PRIiPTR" for printing intptr_t values.   The  length  modifier  for
              intptr_t for the scanf(3) family of functions is expanded by the macros SCNdPTR and
              SCNiPTR, (defined in <inttypes.h>); resulting commonly in %"SCNdPTR" or  %"SCNiPTR"
              for scanning intptr_t values.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: the uintptr_t and void * types in this page.

       lconv
              Include: <locale.h>.

              struct lconv {                  /* Values in the "C" locale: */
                  char   *decimal_point;      /* "." */
                  char   *thousands_sep;      /* "" */
                  char   *grouping;           /* "" */
                  char   *mon_decimal_point;  /* "" */
                  char   *mon_thousands_sep;  /* "" */
                  char   *mon_grouping;       /* "" */
                  char   *positive_sign;      /* "" */
                  char   *negative_sign;      /* "" */
                  char   *currency_symbol;    /* "" */
                  char    frac_digits;        /* CHAR_MAX */
                  char    p_cs_precedes;      /* CHAR_MAX */
                  char    n_cs_precedes;      /* CHAR_MAX */
                  char    p_sep_by_space;     /* CHAR_MAX */
                  char    n_sep_by_space;     /* CHAR_MAX */
                  char    p_sign_posn;        /* CHAR_MAX */
                  char    n_sign_posn;        /* CHAR_MAX */
                  char   *int_curr_symbol;    /* "" */
                  char    int_frac_digits;    /* CHAR_MAX */
                  char    int_p_cs_precedes;  /* CHAR_MAX */
                  char    int_n_cs_precedes;  /* CHAR_MAX */
                  char    int_p_sep_by_space; /* CHAR_MAX */
                  char    int_n_sep_by_space; /* CHAR_MAX */
                  char    int_p_sign_posn;    /* CHAR_MAX */
                  char    int_n_sign_posn;    /* CHAR_MAX */
              };

              Contains  members  related to the formatting of numeric values.  In the "C" locale,
              its members have the values shown in the comments above.

              Conforming to: C11 and later; POSIX.1-2001 and later.

              See also: setlocale(3), localeconv(3), charsets(7), locale(7)

       ldiv_t
              Include: <stdlib.h>.

              typedef struct {
                  long    quot; /* Quotient */
                  long    rem;  /* Remainder */
              } ldiv_t;

              It is the type of the value returned by the ldiv(3) function.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: ldiv(3)

       lldiv_t
              Include: <stdlib.h>.

              typedef struct {
                  long long   quot; /* Quotient */
                  long long   rem;  /* Remainder */
              } lldiv_t;

              It is the type of the value returned by the lldiv(3) function.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: lldiv(3)

       mode_t
              Include:   <sys/types.h>.    Alternatively,   <fcntl.h>,    <ndbm.h>,    <spawn.h>,
              <sys/ipc.h>, <sys/mman.h>, or <sys/stat.h>.

              Used  for  some file attributes (e.g., file mode).  According to POSIX, it shall be
              an integer type.

              Conforming to: POSIX.1-2001 and later.

              See also: chmod(2), mkdir(2), open(2), stat(2), umask(2)

       off64_t
              Include: <sys/types.h>.

              Used for file sizes.  It is a 64-bit signed integer type.

              Conforming to: Present in glibc.  It is not standardized by the C language standard
              nor POSIX.

              Notes:  The  feature test macro _LARGEFILE64_SOURCE has to be defined for this type
              to be available.

              See  also:  copy_file_range(2),   readahead(2),   sync_file_range(2),   lseek64(3),
              feature_test_macros(7)

              See also the off_t type in this page.

       off_t
              Include:    <sys/types.h>.     Alternatively,    <aio.h>,   <fcntl.h>,   <stdio.h>,
              <sys/mman.h>, <sys/stat.h.h>, or <unistd.h>.

              Used for file sizes.  According to POSIX, this shall be a signed integer type.

              Versions: <aio.h> and <stdio.h> define off_t since POSIX.1-2008.

              Conforming to: POSIX.1-2001 and later.

              Notes: On some architectures, the width of this type can  be  controlled  with  the
              feature test macro _FILE_OFFSET_BITS.

              See  also:  lseek(2),  mmap(2), posix_fadvise(2), pread(2), truncate(2), fseeko(3),
              lockf(3), posix_fallocate(3), feature_test_macros(7)

              See also the off64_t type in this page.

       pid_t
              Include:   <sys/types.h>.    Alternatively,   <fcntl.h>,   <sched.h>,   <signal.h>,
              <spawn.h>,   <sys/msg.h>,   <sys/sem.h>,  <sys/shm.h>,  <sys/wait.h>,  <termios.h>,
              <time.h>, <unistd.h>, or <utmpx.h>.

              This type is used for storing process IDs, process  group  IDs,  and  session  IDs.
              According to POSIX, it shall be a signed integer type, and the implementation shall
              support one or more programming environments where the width of pid_t is no greater
              than the width of the type long.

              Conforming to: POSIX.1-2001 and later.

              See   also:  fork(2),  getpid(2),  getppid(2),  getsid(2),  gettid(2),  getpgid(2),
              kill(2),    pidfd_open(2),    sched_setscheduler(2),    waitpid(2),    sigqueue(3),
              credentials(7),

       ptrdiff_t
              Include: <stddef.h>.

              Used  for  a count of elements, and array indices.  It is the result of subtracting
              two pointers.  According to the C language standard, it shall be a  signed  integer
              type capable of storing values in the range [PTRDIFF_MIN, PTRDIFF_MAX].

              The  length  modifier  for ptrdiff_t for the printf(3) and the scanf(3) families of
              functions is t; resulting commonly in %td or %ti for printing ptrdiff_t values.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: the size_t and ssize_t types in this page.

       regex_t
              Include: <regex.h>.

              typedef struct {
                  size_t  re_nsub; /* Number of parenthesized subexpressions */
              } regex_t;

              This is a structure type used in regular expression matching.  It holds a  compiled
              regular expression, compiled with regcomp(3).

              Conforming to: POSIX.1-2001 and later.

              See also: regex(3)

       regmatch_t
              Include: <regex.h>.

              typedef struct {
                  regoff_t    rm_so; /* Byte offset from start of string
                                        to start of substring */
                  regoff_t    rm_eo; /* Byte offset from start of string of
                                        the first character after the end of
                                        substring */
              } regmatch_t;

              This is a structure type used in regular expression matching.

              Conforming to: POSIX.1-2001 and later.

              See also: regexec(3)

       regoff_t
              Include: <regex.h>.

              According  to  POSIX,  it  shall  be  a  signed integer type capable of storing the
              largest value that can be stored in either a ptrdiff_t type or a ssize_t type.

              Versions: Prior to POSIX.1-2008, the type was capable of storing the largest  value
              that can be stored in either an off_t type or a ssize_t type.

              Conforming to: POSIX.1-2001 and later.

              See  also:  the  regmatch_t  structure  and the ptrdiff_t and ssize_t types in this
              page.

       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.

       size_t
              Include: <stddef.h> or <sys/types.h>.  Alternatively, <aio.h>,  <glob.h>,  <grp.h>,
              <iconv.h>,  <monetary.h>,  <mqueue.h>,  <ndbm.h>,  <pwd.h>,  <regex.h>, <search.h>,
              <signal.h>,   <stdio.h>,   <stdlib.h>,   <string.h>,   <strings.h>,   <sys/mman.h>,
              <sys/msg.h>,   <sys/sem.h>,  <sys/shm.h>,  <sys/socket.h>,  <sys/uio.h>,  <time.h>,
              <unistd.h>, <wchar.h>, or <wordexp.h>.

              Used for a count of bytes.  It is the result of the sizeof operator.  According  to
              the  C  language  standard, it shall be an unsigned integer type capable of storing
              values in the range [0, SIZE_MAX].  According to POSIX,  the  implementation  shall
              support  one  or  more  programming  environments  where  the width of size_t is no
              greater than the width of the type long.

              The length modifier for size_t for the  printf(3)  and  the  scanf(3)  families  of
              functions is z; resulting commonly in %zu or %zx for printing size_t values.

              Versions:  <aio.h>,  <glob.h>, <grp.h>, <iconv.h>, <mqueue.h>, <pwd.h>, <signal.h>,
              and <sys/socket.h> define size_t since POSIX.1-2008.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: read(2), write(2), fread(3), fwrite(3), memcmp(3), memcpy(3),  memset(3),
              offsetof(3)

              See also the ptrdiff_t and ssize_t types in this page.

       sockaddr
              Include: <sys/socket.h>.

              struct sockaddr {
                  sa_family_t sa_family; /* Address family */
                  char        sa_data[]; /* Socket address */
              };

              Describes a socket address.

              Conforming to: POSIX.1-2001 and later.

              See also: accept(2), getpeername(2), getsockname(2), socket(2)

       socklen_t
              Include: <sys/socket.h>.  Alternatively, <netdb.h>.

              Describes  the  length  of  a socket address.  According to POSIX, this shall be an
              integer type of at least 32 bits.

              Conforming to: POSIX.1-2001 and later.

              See  also:  accept(2),  bind(2),  connect(2),   gethostbyaddr(2),   getnameinfo(2),
              socket(2)

              See also the sockaddr structure in this page.

       ssize_t
              Include:   <sys/types.h>.    Alternatively,   <aio.h>,   <monetary.h>,  <mqueue.h>,
              <stdio.h>, <sys/msg.h>, <sys/socket.h>, <sys/uio.h>, or <unistd.h>.

              Used for a count of bytes or an error indication.  According to POSIX, it shall  be
              a  signed  integer  type  capable  of  storing  values  at  least in the range [-1,
              SSIZE_MAX],  and  the  implementation  shall  support  one  or   more   programming
              environments  where  the  width of ssize_t is no greater than the width of the type
              long.

              Glibc and most other implementations provide a length modifier for ssize_t for  the
              printf(3) and the scanf(3) families of functions, which is z; resulting commonly in
              %zd or %zi for printing ssize_t values.  Although  z  works  for  ssize_t  on  most
              implementations,  portable  POSIX  programs  should  avoid using it—for example, by
              converting the value to intmax_t and using its length modifier (j).

              Conforming to: POSIX.1-2001 and later.

              See also: read(2), readlink(2), readv(2), recv(2), send(2), write(2)

              See also the ptrdiff_t and size_t types in this page.

       suseconds_t
              Include: <sys/types.h>.  Alternatively, <sys/select.h>, or <sys/time.h>.

              Used for time in microseconds.  According to POSIX, it shall be  a  signed  integer
              type  capable  of  storing  values  at  least  in  the range [-1, 1000000], and the
              implementation shall support one or more programming environments where  the  width
              of suseconds_t is no greater than the width of the type long.

              Conforming to: POSIX.1-2001 and later.

              See also: the timeval structure in this page.

       time_t
              Include:   <time.h>   or  <sys/types.h>.   Alternatively,  <sched.h>,  <sys/msg.h>,
              <sys/select.h>, <sys/sem.h>, <sys/shm.h>, <sys/stat.h>, <sys/time.h>, or <utime.h>.

              Used for time in seconds.  According to POSIX, it shall be an integer type.

              Versions: <sched.h> defines time_t since POSIX.1-2008.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: stime(2), time(2), ctime(3), difftime(3)

       timer_t
              Include: <sys/types.h>.  Alternatively, <time.h>.

              Used for timer ID returned by timer_create(2).  According to POSIX,  there  are  no
              defined comparison or assignment operators for this type.

              Conforming to: POSIX.1-2001 and later.

              See also: timer_create(2), timer_delete(2), timer_getoverrun(2), timer_settime(2)

       timespec
              Include:  <time.h>.   Alternatively,  <aio.h>,  <mqueue.h>,  <sched.h>, <signal.h>,
              <sys/select.h>, or <sys/stat.h>.

              struct timespec {
                  time_t  tv_sec;  /* Seconds */
                  long    tv_nsec; /* Nanoseconds */
              };

              Describes times in seconds and nanoseconds.

              Conforming to: C11 and later; POSIX.1-2001 and later.

              See also: clock_gettime(2), clock_nanosleep(2),  nanosleep(2),  timerfd_gettime(2),
              timer_gettime(2)

       timeval
              Include:   <sys/time.h>.    Alternatively,   <sys/resource.h>,  <sys/select.h>,  or
              <utmpx.h>.

              struct timeval {
                  time_t      tv_sec;  /* Seconds */
                  suseconds_t tv_usec; /* Microseconds */
              };

              Describes times in seconds and microseconds.

              Conforming to: POSIX.1-2001 and later.

              See  also:   gettimeofday(2),   select(2),   utimes(2),   adjtime(3),   futimes(3),
              timeradd(3)

       uid_t
              Include:   <sys/types.h>.    Alternatively,   <pwd.h>,   <signal.h>,   <stropts.h>,
              <sys/ipc.h>, <sys/stat.h>, or <unistd.h>.

              A type used to hold user IDs.  According to POSIX, this shall be an integer type.

              Conforming to: POSIX.1-2001 and later.

              See   also:   chown(2),   getuid(2),   geteuid(2),    getresuid(2),    getpwnam(3),
              credentials(7)

       uintmax_t
              Include: <stdint.h>.  Alternatively, <inttypes.h>.

              An  unsigned integer type capable of representing any value of any unsigned integer
              type supported by the implementation.  According to the  C  language  standard,  it
              shall be capable of storing values in the range [0, UINTMAX_MAX].

              The  macro  UINTMAX_C()  expands  its  argument  to  an  integer  constant  of type
              uintmax_t.

              The length modifier for uintmax_t for the printf(3) and the  scanf(3)  families  of
              functions is j; resulting commonly in %ju or %jx for printing uintmax_t values.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              Bugs:  uintmax_t  is not large enough to represent values of type unsigned __int128
              in implementations where unsigned __int128 is defined and  unsigned  long  long  is
              less than 128 bits wide.

              See also: the intmax_t type in this page.

       uintN_t
              Include: <stdint.h>.  Alternatively, <inttypes.h>.

              uint8_t, uint16_t, uint32_t, uint64_t

              An  unsigned  integer  type  of  a fixed width of exactly N bits, N being the value
              specified in its type name.  According to the C language standard,  they  shall  be
              capable  of  storing  values  in  the  range  [0, UINTN_MAX], substituting N by the
              appropriate number.

              According to POSIX, uint8_t, uint16_t, and uint32_t are required; uint64_t is  only
              required in implementations that provide integer types with width 64; and all other
              types of this form are optional.

              The length modifiers for the uintN_t types for the printf(3)  family  of  functions
              are  expanded  by  macros  of  the forms PRIuN, PRIoN, PRIxN, and PRIXN (defined in
              <inttypes.h>); resulting  for  example  in  %"PRIu32"  or  %"PRIx32"  for  printing
              uint32_t  values.   The  length  modifiers  for  the uintN_t types for the scanf(3)
              family of functions are expanded by macros of the forms SCNuN,  SCNoN,  SCNxN,  and
              SCNXN  (defined  in  <inttypes.h>); resulting for example in %"SCNu16" or %"SCNx16"
              for scanning uint16_t values.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: the intmax_t, intN_t, and uintmax_t types in this page.

       uintptr_t
              Include: <stdint.h>.  Alternatively, <inttypes.h>.

              An unsigned integer type such that any valid (void *) value  can  be  converted  to
              this  type  and back.  According to the C language standard, it shall be capable of
              storing values in the range [0, UINTPTR_MAX].

              The length modifier for uintptr_t for the printf(3) family of functions is expanded
              by  the  macros  PRIuPTR,  PRIoPTR, PRIxPTR, and PRIXPTR (defined in <inttypes.h>);
              resulting commonly in %"PRIuPTR" or %"PRIxPTR" for printing uintptr_t values.   The
              length  modifier  for uintptr_t for the scanf(3) family of functions is expanded by
              the macros SCNuPTR,  SCNoPTR,  SCNxPTR,  and  SCNXPTR  (defined  in  <inttypes.h>);
              resulting commonly in %"SCNuPTR" or %"SCNxPTR" for scanning uintptr_t values.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: the intptr_t and void * types in this page.

       va_list
              Include: <stdarg>.  Alternatively, <stdio.h>, or <wchar.h>.

              Used  by  functions  with  a  varying  number  of  arguments of varying types.  The
              function must declare an object of  type  va_list  which  is  used  by  the  macros
              va_start(3),   va_arg(3),  va_copy(3),  and  va_end(3)  to  traverse  the  list  of
              arguments.

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: va_start(3), va_arg(3), va_copy(3), va_end(3)

       void *
              According to the C language standard, a pointer to any object type may be converted
              to  a pointer to void and back.  POSIX further requires that any pointer, including
              pointers to functions, may be converted to a pointer to void and back.

              Conversions from and to any other pointer type are done implicitly,  not  requiring
              casts  at  all.   Note  that  this  feature prevents any kind of type checking: the
              programmer should be careful not to convert a void * value to a  type  incompatible
              to that of the underlying data, because that would result in undefined behavior.

              This type is useful in function parameters and return value to allow passing values
              of any type.  The function will typically use some mechanism to know the real  type
              of the data being passed via a pointer to void.

              A  value of this type can't be dereferenced, as it would give a value of type void,
              which is not possible.  Likewise, pointer arithmetic  is  not  possible  with  this
              type.   However,  in  GNU  C,  pointer arithmetic is allowed as an extension to the
              standard; this is done by treating the size of a void or of a  function  as  1.   A
              consequence  of  this is that sizeof is also allowed on void and on function types,
              and returns 1.

              The conversion specifier for void * for the printf(3) and the scanf(3) families  of
              functions is p.

              Versions:  The  POSIX  requirement  about compatibility between void * and function
              pointers was added in POSIX.1-2008 Technical Corrigendum 1 (2013).

              Conforming to: C99 and later; POSIX.1-2001 and later.

              See also: malloc(3), memcmp(3), memcpy(3), memset(3)

              See also the intptr_t and uintptr_t types 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)

COLOPHON

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