atoq(3) - f39

1atoi(3)                    Library Functions Manual                    atoi(3)
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NAME

6       atoi, atol, atoll - convert a string to an integer
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <stdlib.h>
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14       int atoi(const char *nptr);
15       long atol(const char *nptr);
16       long long atoll(const char *nptr);
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18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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20       atoll():
21           _ISOC99_SOURCE
22               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

25       The  atoi() function converts the initial portion of the string pointed
26       to by nptr to int.  The behavior is the same as
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28           strtol(nptr, NULL, 10);
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30       except that atoi() does not detect errors.
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32       The atol() and atoll() functions behave the same as atoi(), except that
33       they  convert the initial portion of the string to their return type of
34       long or long long.
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RETURN VALUE

37       The converted value or 0 on error.
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ATTRIBUTES

40       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
41       tributes(7).
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43       ┌─────────────────────────────────────┬───────────────┬────────────────┐
44       │Interface                            │ Attribute     │ Value          │
45       ├─────────────────────────────────────┼───────────────┼────────────────┤
46       │atoi(), atol(), atoll()              │ Thread safety │ MT-Safe locale │
47       └─────────────────────────────────────┴───────────────┴────────────────┘
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VERSIONS

50       POSIX.1  leaves  the  return  value of atoi() on error unspecified.  On
51       glibc, musl libc, and uClibc, 0 is returned on error.
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STANDARDS

54       C11, POSIX.1-2008.
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HISTORY

57       C99, POSIX.1-2001, SVr4, 4.3BSD.
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59       C89 and POSIX.1-1996 include the functions atoi() and atol() only.
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BUGS

62       errno is not set on error so there is no way to distinguish  between  0
63       as  an  error  and  as  the converted value.  No checks for overflow or
64       underflow are done.  Only  base-10  input  can  be  converted.   It  is
65       recommended  to  instead  use  the  strtol()  and  strtoul()  family of
66       functions in new programs.
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