1STRTOU(3bsd) LOCAL STRTOU(3bsd)
2
4 strtou — convert a string to an uintmax_t integer
5
7 Utility functions from BSD systems (libbsd, -lbsd)
8
10 #include <inttypes.h>
11 (See libbsd(7) for include usage.)
12 uintmax_t
14 strtou(const char * restrict nptr, char ** restrict endptr, int base,
15 uintmax_t lo, uintmax_t hi, int *rstatus);
16
18 The strtou() function converts the string in nptr to an uintmax_t value.
19 The strtou() function uses internally strtoumax(3) and ensures that the
20 result is always in the range [ lo .. hi ]. In adddition it always
21 places 0 on success or a conversion status in the rstatus argument,
22 avoiding the errno gymnastics the other functions require. The rstatus
23 argument can be NULL if conversion status is to be ignored.
24 The string may begin with an arbitrary amount of white space (as deter‐
26 mined by isspace(3)) followed by a single optional ‘+’ or ‘-’ sign. If
27 base is zero or 16, the string may then include a ‘0x’ or ‘0X’ prefix,
28 and the number will be read in base 16; otherwise, a zero base is taken
29 as 10 (decimal) unless the next character is ‘0’, in which case it is
30 taken as 8 (octal).
31 The remainder of the string is converted to an uintmax_t value in the
33 obvious manner, stopping at the end of the string or at the first charac‐
34 ter that does not produce a valid digit in the given base. (In bases
35 above 10, the letter ‘A’ in either upper or lower case represents 10, ‘B’
36 represents 11, and so forth, with ‘Z’ representing 35.)
37 If endptr is non-nil, strtou() stores the address of the first invalid
39 character in *endptr. If there were no digits at all, however, strtou()
40 stores the original value of nptr in *endptr. (Thus, if *nptr is not
41 ‘\0’ but **endptr is ‘\0’ on return, the entire string was valid.)
42
44 The strtou() function always returns the closest value in the range spec‐
45 ified by the lo and hi arguments.
46 The errno value is guaranteed to be left unchanged.
48 Errors are stored as the conversion status in the rstatus argument.
50
52 The following example will always return a number in [1..99] range no
53 matter what the input is, and warn if the conversion failed.
54 int e;
56 uintmax_t lval = strtou(buf, NULL, 0, 1, 99, &e);
57 if (e)
58 warnc(e, "conversion of `%s' to a number failed, using %ju",
59 buf, lval);
60
62 [ECANCELED] The string did not contain any characters that were
63 converted.
64 [EINVAL] The base is not between 2 and 36 and does not contain
66 the special value 0.
67 [ENOTSUP] The string contained non-numeric characters that did
69 not get converted. In this case, endptr points to the
70 first unconverted character.
71 [ERANGE] The given string was out of range; the value converted
73 has been clamped; or the range given was invalid, i.e.
74 lo > hi.
75
77 atof(3), atoi(3), atol(3), atoll(3), strtod(3), strtoi(3bsd),
78 strtoimax(3), strtol(3), strtoll(3), strtoul(3), strtoull(3),
79 strtoumax(3)
80
82 The strtou() function is a NetBSD extension.
83
85 The strtou() function first appeared in NetBSD 7. OpenBSD introduced the
86 strtonum(3bsd) function for the same purpose, but the interface makes it
87 impossible to properly differentiate illegal returns.
88
90 Ignores the current locale.
91BSD November 13, 2015 BSD