STRTOL(3) OpenBSD Programmer's Manual STRTOL(3)NAME
strtol, strtoll, strtoimax, strtoq, - convert string value to a long,
long long or intmax_t integer
SYNOPSIS
#include <limits.h>
#include <stdlib.h>
long
strtol(const char *nptr, char **endptr, int base);
long long
strtoll(const char *nptr, char **endptr, int base);
#include <inttypes.h>
intmax_t
strtoimax(const char *nptr, char **endptr, int base);
#include <sys/types.h>
#include <limits.h>
#include <stdlib.h>
quad_t
strtoq(const char *nptr, char **endptr, int base);
DESCRIPTION
The strtol() function converts the string in nptr to a long value. The
strtoll() function converts the string in nptr to a long long value. The
strtoimax() function converts the string in nptr to an intmax_t value.
The strtoq() function is a deprecated equivalent of strtoll() and is
provided for backwards compatibility with legacy programs. The
conversion is done according to the given base, which must be a number
between 2 and 36 inclusive or the special value 0.
The string may begin with an arbitrary amount of whitespace (as
determined by isspace(3)) followed by a single optional `+' or `-' sign.
If base is zero or 16, the string may then include a `0x' prefix, and the
number will be read in base 16; otherwise, a zero base is taken as 10
(decimal) unless the next character is `0', in which case it is taken as
8 (octal).
The remainder of the string is converted to a long, long long, or
intmax_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 `A' in either upper or lower case represents 10, `B' represents
11, and so forth, with `Z' representing 35.)
If endptr is non-null, strtol() stores the address of the first invalid
character in *endptr. If there were no digits at all, however, strtol()
stores the original value of nptr in *endptr. (Thus, if *nptr is not
`\0' but **endptr is `\0' on return, the entire string was valid.)
RETURN VALUES
The strtol(), strtoll(), strtoimax(), and strtoq() functions return the
result of the conversion, unless the value would underflow or overflow.
If no conversion could be performed, 0 is returned; the global variable
errno is also set to EINVAL, though this is not portable across all
platforms. If overflow or underflow occurs, errno is set to ERANGE and
the function return value is as follows:
Function underflow overflow
strtol() LONG_MIN LONG_MAX
strtoll() LLONG_MIN LLONG_MAX
strtoimax() INTMAX_MIN INTMAX_MAX
strtoq() LLONG_MIN LLONG_MAX
EXAMPLES
Ensuring that a string is a valid number (i.e., in range and containing
no trailing characters) requires clearing errno beforehand explicitly
since errno is not changed on a successful call to strtol(), and the
return value of strtol() cannot be used unambiguously to signal an error:
char *ep;
long lval;
...
errno = 0;
lval = strtol(buf, &ep, 10);
if (buf[0] == '\0' || *ep != '\0')
goto not_a_number;
if (errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN))
goto out_of_range;
This example will accept ``12'' but not ``12foo'' or ``12\n''. If
trailing whitespace is acceptable, further checks must be done on *ep;
alternately, use sscanf(3).
If strtol() is being used instead of atoi(3), error checking is further
complicated because the desired return value is an int rather than a
long; however, on some architectures integers and long integers are the
same size. Thus the following is necessary:
char *ep;
int ival;
long lval;
...
errno = 0;
lval = strtol(buf, &ep, 10);
if (buf[0] == '\0' || *ep != '\0')
goto not_a_number;
if ((errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN)) ||
(lval > INT_MAX || lval < INT_MIN))
goto out_of_range;
ival = lval;
ERRORS
[ERANGE] The given string was out of range; the value converted has
been clamped.
SEE ALSOatof(3), atoi(3), atol(3), atoll(3), sscanf(3), strtod(3), strtonum(3),
strtoul(3)STANDARDS
The strtol(), strtoll(), and strtoimax() functions conform to
ANSI/ISO/IEC 9899-1999 (``ANSI C99''). The strtoq() function is a BSD
extension and is provided for backwards compatibility with legacy
programs.
BUGS
Ignores the current locale.
OpenBSD 4.9 November 13, 2007 OpenBSD 4.9
