SYSTEM_DATA_TYPES(7)      (2020-12-21)       SYSTEM_DATA_TYPES(7)

     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)

          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 func-
               tions.  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)

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          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

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               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 environ-
               ment, 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.

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               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(2), 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 implementa-
               tion.  According to the C language standard, it shall
               be capable of storing values in the range [INTMAX_MIN,
               INTMAX_MAX].

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               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 com-
               monly 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.

          _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.  Accord-
               ing to the C language standard, it shall be capable of

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               storing values in the range [INTPTR_MIN, INTPTR_MAX].

               The length modifier for intptr_t for the printf(3) fam-
               ily of functions is expanded by the macros PRIdPTR and
               PRIiPTR (defined in <inttypes.h>); resulting commonly
               in %"PRIdPTR" or %"PRIiPTR" for printing intptr_t val-
               ues.  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 com-
               monly 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.

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               See also: setlocale(3), localeconv(3), charsets(5),
               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)

          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),

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               posix_fallocate(3), feature_test_macros(7)

          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 com-
               monly 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, com-
               piled with regcomp(3).

               Conforming to: POSIX.1-2001 and later.

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               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).

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               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 struc-
               ture 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 */

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                   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 program-
               ming 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 com-
               monly 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.

          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,

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               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 val-
               ues at least in the range [-1, 1000000], and the imple-
               mentation shall support one or more programming envi-
               ronments 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>.

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               Used for timer ID returned by timer_create(2).  Accord-
               ing 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),

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               getresuid(2), getpwnam(2), 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 inte-
               ger 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 com-
               monly 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.

          _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

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               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.  Accord-
               ing 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 func-
               tions is expanded by the macros SCNuPTR, SCNoPTR,
               SCNxPTR, and SCNXPTR (defined in <inttypes.h>); result-
               ing 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, includ-
               ing pointers to functions, may be converted to a
               pointer to void and back.

               Conversions from and to any other pointer type are done

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               implicitly, not requiring casts at all.  Note that this
               feature prevents any kind of type checking: the pro-
               grammer 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 func-
               tion 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 treat-
               ing the size of a void or of a function as 1.  A conse-
               quence 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 par-
          ticular 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 lim-
          its, 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.

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        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 speci-
          fied 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 stan-
          dards.  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 aqusaq */

              us = tmp;

              /* Even though suseconds_t can hold the value -1, this isnaqt
                 a sensible number of microseconds */

              if (us < 0) {
                  fprintf(stderr, "Scanned value shouldnaqt be negative!n");
                  exit(EXIT_FAILURE);

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              }

              /* 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
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

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