libc/stdlib/strtoi.3

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.\"     from: @(#)strtol.3	8.1 (Berkeley) 6/4/93
.\"
.\" Created by Kamil Rytarowski, based on ID:
.\" NetBSD: strtol.3,v 1.31 2015/03/11 09:57:35 wiz Exp
.\"
.Dd July 24, 2024
.Dt STRTOI 3
.Os
.Sh NAME
.Nm strtoi ,
.Nm strtoi_l
.Nd convert a string value to an intmax_t integer
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In inttypes.h
.Ft intmax_t
.Fo strtoi
.Fa "const char * restrict nptr"
.Fa "char ** restrict endptr"
.Fa "int base"
.Fa "intmax_t lo"
.Fa "intmax_t hi"
.Fa "int *rstatus"
.Fc
.In locale.h
.Ft intmax_t
.Fo strtoi_l
.Fa "const char * restrict nptr"
.Fa "char ** restrict endptr"
.Fa "int base"
.Fa "intmax_t lo"
.Fa "intmax_t hi"
.Fa "int *rstatus"
.Fa "locale_t loc"
.Fc
.Sh DESCRIPTION
The
.Fn strtoi
generates the
.Ft intmax_t
result value equivalent to the numeric string in
.Fa nptr .
The
.Fn strtoi
function internally uses
.Xr strtoimax 3
and then ensures that the result is in the range
.Bq Fa lo No .. Fa hi .
In addition it places
a conversion status indicator,
.Dv 0
if fully successful,
in the integer addressed by the
.Fa rstatus
argument, if that is not NULL, allowing the
.Dv errno
gymnastics that other similar functions require to be avoided.
The
.Fa rstatus
argument can be
.Dv NULL
if the conversion status is to be ignored.
.Pp
The operation of
.Fn strtoi
is unspecified if
.Fa lo
is greater than
.Fa hi .
.Pp
The string may begin with an arbitrary amount of white space
(as determined by
.Xr isspace 3 )
followed by a single optional
.Ql +
or
.Ql -
sign.
If
.Fa base
is zero or 16,
the string may then include a
.Ql 0x
or
.Ql 0X
prefix,
after which there must immediately follow at least one hexadecimal digit,
and the number will be read in base 16; otherwise,
.\" if the
.\" .Fa base
.\" is zero or 2,
.\" the string may then include a
.\" .Ql 0b
.\" or
.\" .Ql 0B
.\" prefix,
.\" and the number will be read in base 2; otherwise,
a zero
.Fa base
is taken as 10 (decimal) unless the next character is
.Ql 0 ,
in which case it is taken as 8 (octal).
.Pp
The remainder of the string is converted to the
.Em intmax_t
result in the obvious manner,
stopping at the end of the string
or at the first character which is not a valid digit
in the given base.
(In bases above 10, the letter
.Ql A
in either upper or lower case
represents 10,
.Ql B
represents 11, and so forth, with
.Ql Z
representing 35.)
.Pp
If
.Fa endptr
is not NULL,
.Fn strtoi
stores the address of the first character after those
which were converted in
.Fa *endptr .
If there were no digits at all, however,
or if the
.Fa base
is invalid,
.Fn strtoi
stores the original value of
.Fa nptr
in
.Fa *endptr .
(Thus, if
.Fa *nptr
is not
.Ql \e0
but
.Fa **endptr
is
.Ql \e0
on return, the entire string was valid.)
Note that converting an out of range value has no
impact upon the value placed into
.Fa *endptr .
.Pp
The
.Fn strtoi_l
function is identical, except uses the locale given by
.Fa loc
rather than the current locale, when determining what is white space to
be skipped before the conversion begins.
.Sh RETURN VALUES
The
.Fn strtoi
function,
returns the converted value,
or the closest value in the range specified by the
.Fa lo
and
.Fa hi
arguments, if the value converted was outside that range.
If
.Fa lo
is equal to
.Fa hi
and no overriding error occurs,
that value will always be returned.
.Pp
The
.Va errno
value from
.In errno.h ,
is guaranteed to be left unchanged.
.Pp
Errors are stored as the conversion status error indicator,
taken from a subset of the values from
.In errno.h
in the
.Fa rstatus
argument, if that was not given as a NULL pointer.
See the ERRORS section below for the possible values.
.Sh EXAMPLES
The following example will always return a number in
.Dv [1..99]
range no matter what the input is, and warn if the conversion failed.
.Bd -literal -offset indent
int e;
intmax_t lval = strtoi(buf, NULL, 0, 1, 99, &e);
if (e)
	warnc(e, "conversion of `%s' to a number failed, using %jd",
	    buf, lval);
.Ed
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ECANCELED
The string did not contain any characters that were converted.
If given
.Fa endptr
will be set to
.Fa nptr .
.It Bq Er EINVAL
The
.Ar base
is not between 2 and 36 and nor is it the special value 0.
If given
.Fa endptr
will be set to
.Fa nptr .
.It Bq Er ENOTSUP
The string contained non-numeric characters that did not get converted.
In this case,
.Fa endptr
points to the first unconverted character.
.It Bq Er ERANGE
The given string was out of range; the value converted has been clamped.
In this case,
.Fa endptr
points to the terminating
.Sq \e0
if the
.Fa nptr
string was fully converted, or to the first unconverted character otherwise.
.El
.Pp
The validity of the provided base is checked first, and if that
fails, no further processing is attempted.
The range check is more important than the unconverted characters check,
and is given priority.
If a program needs to know if there were unconverted characters when an
out of range number has been provided, it needs to supply and test
.Fa endptr.
.Sh SEE ALSO
.Xr atof 3 ,
.Xr atoi 3 ,
.Xr atol 3 ,
.Xr atoll 3 ,
.Xr strtod 3 ,
.Xr strtou 3 ,
.Xr strtoimax 3 ,
.Xr strtol 3 ,
.Xr strtoll 3 ,
.Xr strtoul 3 ,
.Xr strtoull 3 ,
.Xr warnc 3
.Sh STANDARDS
The
.Fn strtoi
and
.Fn strtoi_l
functions are a
.Nx
extension.
.Sh HISTORY
The
.Fn strtoi
function first appeared in
.Nx 7 .
.Ox
introduced the
.Fn strtonum 3
function for the same purpose, but its interface makes it impossible to
properly differentiate error conditions.
.Sh BUGS
Ignores the current locale while doing the numeric conversion, only
ASCII letters and digits are allowed, and no grouping characters.