xref: /freebsd/lib/libc/stdlib/strtoul.3 (revision afe61c15161c324a7af299a9b8457aba5afc92db)
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36.\"     @(#)strtoul.3	8.1 (Berkeley) 6/4/93
37.\"
38.Dd June 4, 1993
39.Dt STRTOUL 3
40.Os
41.Sh NAME
42.Nm strtoul, strtouq
43.Nd convert a string to an unsigned long or uquad_t integer
44.Sh SYNOPSIS
45.Fd #include <stdlib.h>
46.Fd #include <limits.h>
47.Ft unsigned long
48.Fn strtoul "const char *nptr" "char **endptr" "int base"
49
50.Fd #include <sys/types.h>
51.Fd #include <stdlib.h>
52.Fd #include <limits.h>
53.Ft u_quad_t
54.Fn strtouq "const char *nptr" "char **endptr" "int base"
55.Sh DESCRIPTION
56The
57.Fn strtoul
58function
59converts the string in
60.Fa nptr
61to an
62.Em unsigned long
63value.
64The
65.Fn strtouq
66function
67converts the string in
68.Fa nptr
69to a
70.Em u_quad_t
71value.
72The conversion is done according to the given
73.Fa base ,
74which must be between 2 and 36 inclusive,
75or be the special value 0.
76.Pp
77The string may begin with an arbitrary amount of white space
78(as determined by
79.Xr isspace 3 )
80followed by a single optional
81.Ql +
82or
83.Ql -
84sign.
85If
86.Fa base
87is zero or 16,
88the string may then include a
89.Ql 0x
90prefix,
91and the number will be read in base 16; otherwise, a zero
92.Fa base
93is taken as 10 (decimal) unless the next character is
94.Ql 0 ,
95in which case it is taken as 8 (octal).
96.Pp
97The remainder of the string is converted to an
98.Em unsigned long
99value in the obvious manner,
100stopping at the end of the string
101or at the first character that does not produce a valid digit
102in the given base.
103(In bases above 10, the letter
104.Ql A
105in either upper or lower case
106represents 10,
107.Ql B
108represents 11, and so forth, with
109.Ql Z
110representing 35.)
111.Pp
112If
113.Fa endptr
114is non nil,
115.Fn strtoul
116stores the address of the first invalid character in
117.Fa *endptr .
118If there were no digits at all, however,
119.Fn strtoul
120stores the original value of
121.Fa nptr
122in
123.Fa *endptr .
124(Thus, if
125.Fa *nptr
126is not
127.Ql \e0
128but
129.Fa **endptr
130is
131.Ql \e0
132on return, the entire string was valid.)
133.Sh RETURN VALUES
134The
135.Fn strtoul
136function
137returns either the result of the conversion
138or, if there was a leading minus sign,
139the negation of the result of the conversion,
140unless the original (non-negated) value would overflow;
141in the latter case,
142.Fn strtoul
143returns
144.Dv ULONG_MAX
145and sets the global variable
146.Va errno
147to
148.Er ERANGE .
149.Sh ERRORS
150.Bl -tag -width [ERANGE]
151.It Bq Er ERANGE
152The given string was out of range; the value converted has been clamped.
153.El
154.Sh SEE ALSO
155.Xr strtol 3
156.Sh STANDARDS
157The
158.Fn strtoul
159function
160conforms to
161.St -ansiC .
162.Sh BUGS
163Ignores the current locale.
164