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\"     from: @(#)strtol.3       8.1 (Berkeley) 6/4/93
\"
Dd November 4, 2016
Dt STRTOL 3
Os
Sh NAME
Nm strtol ,
Nm strtoll ,
Nm strtoimax ,
Nm strtoq
Nd convert string value to a long, long long, intmax_t or quad_t integer
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In stdlib.h
In limits.h
Ft long int
Fn strtol "const char * restrict nptr" "char ** restrict endptr" "int base"
Ft long long int
Fn strtoll "const char * restrict nptr" "char ** restrict endptr" "int base"
Pp
In inttypes.h
Ft intmax_t
Fn strtoimax "const char * restrict nptr" "char ** restrict endptr" "int base"
Pp
In sys/types.h
In stdlib.h
In limits.h
Ft quad_t
Fn strtoq "const char * restrict nptr" "char ** restrict endptr" "int base"
Sh DESCRIPTION
The
Fn strtol
function
converts the string in
Fa nptr
to a
Ft long int
value.
The
Fn strtoll
function
converts the string in
Fa nptr
to a
Ft long long int
value.
The
Fn strtoimax
function
converts the string in
Fa nptr
to an
Ft intmax_t
value.
The
Fn strtoq
function
converts the string in
Fa nptr
to a
Ft quad_t
value.
Pp
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
Ql 0x
or
Ql 0X
prefix,
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 an appropriate 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 non-nil, the functions store the address of the first invalid character in
Fa *endptr .
If there were no digits at all, however,
the functions store 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
function
returns the result of the conversion,
unless the value would underflow or overflow.
If an underflow occurs,
Fn strtol
returns
Dv LONG_MIN ,
Fn strtoll
returns
Dv LLONG_MIN ,
and
Fn strtoimax
returns
Dv INTMAX_MIN .
If an overflow occurs,
Fn strtol
returns
Dv LONG_MAX ,
Fn strtoll
returns
Dv LLONG_MAX ,
and
Fn strtoimax
returns
Dv INTMAX_MAX .
In these cases,
Va errno
is set to
Er ERANGE .
If the
Fa base
argument is not supported then
Va errno
is set to
Er EINVAL
and the functions return 0.
Pp
If no error occurs,
Va errno
is left unchanged.
This behavior (which is unlike most library functions) is guaranteed
by the pertinent standards.
Sh EXAMPLES
Because the return value of
Fn strtol
cannot be used unambiguously to detect an error,
Va errno
is left unchanged after a successful call.
To ensure that a string is a valid number (i.e., in range and containing no
trailing characters), clear
Va errno
beforehand explicitly, then check it afterwards:
Bd -literal -offset indent
char *ep;
long lval;

\&...

errno = 0;
lval = strtol(buf, &ep, 10);
if (ep == buf)
       goto not_a_number;
if (*ep != '\e0')
       goto trailing_garbage;
if (errno) {
       assert(errno == ERANGE);
       assert(lval == LONG_MAX || lval == LONG_MIN);
       goto out_of_range;
}
Ed
Pp
This example will accept
Dq 12
but not
Dq 12foo
or
Dq 12\en .
If trailing whitespace is acceptable, further checks must be done on
Va *ep ;
alternately, use
Xr sscanf 3 .
Pp
If
Fn strtol
is being used instead of
Xr atoi 3 ,
error checking is further complicated because the desired return value is an
Li int
rather than a
Li long ;
however, on some architectures integers and long integers are the same size.
Thus the following is necessary:
Bd -literal -offset indent
char *ep;
int ival;
long lval;

\&...

errno = 0;
lval = strtol(buf, &ep, 10);
if (ep == buf)
       goto not_a_number;
if (*ep != '\e0')
       goto trailing_garbage;
if (errno == ERANGE || lval < INT_MIN || INT_MAX < lval)
       goto out_of_range;
assert(errno == 0);
assert(INT_MIN <= lval);
assert(lval <= INT_MAX);
ival = lval;
Ed
Sh ERRORS
Bl -tag -width Er
It Bq Er EINVAL
The
Ar base
is not between 2 and 36 and does not contain the special value 0.
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 atoll 3 ,
Xr strtod 3 ,
Xr strtou 3 ,
Xr strtoul 3 ,
Xr strtoull 3 ,
Xr strtoumax 3
Sh STANDARDS
The
Fn strtol
function
conforms to
St -ansiC .
The
Fn strtoll
and
Fn strtoimax
functions conform to
St -isoC-99 .
Pp
The
Fn strtoq
function is a
Bx
legacy function equivalent to
Fn strtoll
and should not be used in a new code.
Sh BUGS
Ignores the current locale.

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