xref: /freebsd/lib/libc/stdlib/strtol.3 (revision dc36d6f9bb1753f3808552f3afd30eda9a7b206a)

.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd August 21, 2023
.Dt STRTOL 3
.Os
.Sh NAME
.Nm strtol , strtoll , strtoimax , strtoq
.Nd "convert a string value to a"
.Vt long , "long long" , intmax_t
or
.Vt quad_t
integer
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.In limits.h
.Ft long
.Fn strtol "const char * restrict nptr" "char ** restrict endptr" "int base"
.Ft long long
.Fn strtoll "const char * restrict nptr" "char ** restrict endptr" "int base"
.In inttypes.h
.Ft intmax_t
.Fn strtoimax "const char * restrict nptr" "char ** restrict endptr" "int base"
.In sys/types.h
.In stdlib.h
.In limits.h
.Ft quad_t
.Fn strtoq "const char *nptr" "char **endptr" "int base"
.Sh DESCRIPTION
The
.Fn strtol
function
converts the string in
.Fa nptr
to a
.Vt long
value.
The
.Fn strtoll
function
converts the string in
.Fa nptr
to a
.Vt "long long"
value.
The
.Fn strtoimax
function
converts the string in
.Fa nptr
to an
.Vt intmax_t
value.
The
.Fn strtoq
function
converts the string in
.Fa nptr
to a
.Vt quad_t
value.
The conversion is done according to the given
.Fa base ,
which must be between 2 and 36 inclusive,
or be the special value 0.
.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
.Dq Li 0b
prefix, and the number will be read in base 2; or it may include a
.Dq Li 0x
prefix,
and the number will be read in base 16; 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 a
.Vt long , "long long" , intmax_t
or
.Vt quad_t
value in the obvious manner,
stopping 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
.Dv NULL ,
.Fn strtol
stores the address of the first invalid character in
.Fa *endptr .
If there were no digits at all, however,
.Fn strtol
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.)
.Sh RETURN VALUES
The
.Fn strtol ,
.Fn strtoll ,
.Fn strtoimax
and
.Fn strtoq
functions
return the result of the conversion,
unless the value would underflow or overflow.
If no conversion could be performed, 0 is returned and
the global variable
.Va errno
is set to
.Er EINVAL
(the last feature is not portable across all platforms).
If an overflow or underflow occurs,
.Va errno
is set to
.Er ERANGE
and the function return value is clamped according
to the following table.
.Bl -column -offset indent ".Fn strtoimax" ".Sy underflow" ".Sy overflow"
.It Sy Function Ta Sy underflow Ta Sy overflow
.It Fn strtol Ta Dv LONG_MIN Ta Dv LONG_MAX
.It Fn strtoll Ta Dv LLONG_MIN Ta Dv LLONG_MAX
.It Fn strtoimax Ta Dv INTMAX_MIN Ta Dv INTMAX_MAX
.It Fn strtoq Ta Dv LLONG_MIN Ta Dv LLONG_MAX
.El
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EINVAL
The value of
.Fa base
is not supported or
no conversion could be performed
(the last feature is not portable across all platforms).
.It Bq Er ERANGE
The given string was out of range; the value converted has been clamped.
.El
.Sh SEE ALSO
.Xr atof 3 ,
.Xr atoi 3 ,
.Xr atol 3 ,
.Xr strtod 3 ,
.Xr strtonum 3 ,
.Xr strtoul 3 ,
.Xr wcstol 3
.Sh STANDARDS
The
.Fn strtol
function
conforms to
.St -isoC .
The
.Fn strtoll
and
.Fn strtoimax
functions
conform to
.St -isoC-99 .
The
.Bx
.Fn strtoq
function is deprecated.