strtouq(3)

1STRTOUL(3)                 Linux Programmer's Manual                STRTOUL(3)
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NAME

6       strtoul, strtoull, strtouq - convert a string to an unsigned long inte‐
7       ger
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SYNOPSIS

10       #include <stdlib.h>
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12       unsigned long int
13       strtoul(const char *nptr, char **endptr, int base);
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15       unsigned long long int
16       strtoull(const char *nptr, char **endptr, int base);
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DESCRIPTION

19       The strtoul() function converts the initial part of the string in  nptr
20       to  an  unsigned  long integer value according to the given base, which
21       must be between 2 and 36 inclusive, or be the special value 0.
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23       The string may begin with an arbitrary amount of white space (as deter‐
24       mined by isspace(3)) followed by a single optional `+' or `-' sign.  If
25       base is zero or 16, the string may then include a `0x' prefix, and  the
26       number  will  be read in base 16; otherwise, a zero base is taken as 10
27       (decimal) unless the next character is `0', in which case it  is  taken
28       as 8 (octal).
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30       The  remainder of the string is converted to an unsigned long int value
31       in the obvious manner, stopping at the first character which is  not  a
32       valid  digit  in the given base.  (In bases above 10, the letter `A' in
33       either upper or lower case represents 10, `B'  represents  11,  and  so
34       forth, with `Z' representing 35.)
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36       If  endptr  is  not  NULL,  strtoul()  stores  the address of the first
37       invalid character in *endptr.  If there were no  digits  at  all,  str‐
38       toul()  stores  the  original value of nptr in *endptr (and returns 0).
39       In particular, if *nptr is not `\0' but **endptr is `\0' on return, the
40       entire string is valid.
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42       The  strtoull()  function  works  just  like the strtoul() function but
43       returns an unsigned long long integer value.
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RETURN VALUE

46       The strtoul() function returns either the result of the conversion  or,
47       if  there  was  a leading minus sign, the negation of the result of the
48       conversion represented as an unsigned value, unless the original  (non-
49       negated)  value  would  overflow; in the latter case, strtoul() returns
50       ULONG_MAX and sets the global variable errno to ERANGE.  Precisely  the
51       same holds for strtoull() (with ULLONG_MAX instead of ULONG_MAX).
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ERRORS

54       EINVAL (not in C99) The given base contains an unsupported value.
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56       ERANGE The resulting value was out of range.
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58       The  implementation  may also set errno to EINVAL in case no conversion
59       was performed (no digits seen, and 0 returned).
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NOTES

62       Since strtoul() can legitimately return 0 or  LONG_MAX  (LLONG_MAX  for
63       strtoull()) on both success and failure, the calling program should set
64       errno to 0 before the call, and then determine if an error occurred  by
65       checking whether errno has a non-zero value after the call.
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67       In  locales  other  than the "C" locale, other strings may be accepted.
68       (For example, the thousands separator of the current locale may be sup‐
69       ported.)
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71       BSD also has
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73           u_quad_t
74           strtouq(const char *nptr, char **endptr, int base);
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76       with completely analogous definition.  Depending on the wordsize of the
77       current architecture, this may be equivalent to strtoull() or  to  str‐
78       toul().
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80       Negative  values  are considered valid input and are silently converted
81       to the equivalent unsigned long value.
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CONFORMING TO

84       strtoul() conforms to SVr4, C89, C99 and POSIX-2001, and strtoull()  to
85       C99 and POSIX.1-2001.
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EXAMPLE

88       See  the example on the strtol(3) manual page; the use of the functions
89       described in this manual page is similar.
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