1ISDIGIT(3P)                POSIX Programmer's Manual               ISDIGIT(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
10

NAME

12       isdigit, isdigit_l — test for a decimal digit
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SYNOPSIS

15       #include <ctype.h>
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17       int isdigit(int c);
18       int isdigit_l(int c, locale_t locale);
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DESCRIPTION

21       For isdigit(): The functionality described on this  reference  page  is
22       aligned  with the ISO C standard. Any conflict between the requirements
23       described here and the ISO C standard is unintentional. This volume  of
24       POSIX.1‐2017 defers to the ISO C standard.
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26       The isdigit() and isdigit_l() functions shall test whether c is a char‐
27       acter of class digit in the current locale, or  in  the  locale  repre‐
28       sented  by  locale,  respectively;  see  the Base Definitions volume of
29       POSIX.1‐2017, Chapter 7, Locale.
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31       The c argument is an int, the value  of  which  the  application  shall
32       ensure is a character representable as an unsigned char or equal to the
33       value of the macro EOF. If the argument has any other value, the behav‐
34       ior is undefined.
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36       The  behavior is undefined if the locale argument to isdigit_l() is the
37       special locale object LC_GLOBAL_LOCALE or is not a valid locale  object
38       handle.
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RETURN VALUE

41       The isdigit() and isdigit_l() functions shall return non-zero if c is a
42       decimal digit; otherwise, they shall return 0.
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ERRORS

45       No errors are defined.
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47       The following sections are informative.
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EXAMPLES

50       None.
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APPLICATION USAGE

53       To ensure applications  portability,  especially  across  natural  lan‐
54       guages,  only  these functions and the functions in the reference pages
55       listed in the SEE ALSO section should be used for character classifica‐
56       tion.
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RATIONALE

59       None.
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FUTURE DIRECTIONS

62       None.
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SEE ALSO

65       isalnum(),   isalpha(),  isblank(),  iscntrl(),  isgraph(),  islower(),
66       isprint(), ispunct(), isspace(), isupper(), isxdigit()
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68       The  Base  Definitions  volume  of  POSIX.1‐2017,  Chapter  7,  Locale,
69       <ctype.h>, <locale.h>
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72       Portions  of  this text are reprinted and reproduced in electronic form
73       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
74       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
75       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
76       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
77       event of any discrepancy between this version and the original IEEE and
78       The  Open Group Standard, the original IEEE and The Open Group Standard
79       is the referee document. The original Standard can be  obtained  online
80       at http://www.opengroup.org/unix/online.html .
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82       Any  typographical  or  formatting  errors that appear in this page are
83       most likely to have been introduced during the conversion of the source
84       files  to  man page format. To report such errors, see https://www.ker‐
85       nel.org/doc/man-pages/reporting_bugs.html .
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89IEEE/The Open Group                  2017                          ISDIGIT(3P)
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