Tribblix: manual page: strtol.3c

STRTOL(3C) Standard C Library Functions STRTOL(3C)

NAME

strtol, strtoll, atol, atoll, atoi, lltostr, ulltostr - string
conversion routines

SYNOPSIS

#include <stdlib.h>

long strtol(const char *restrict str, char **restrict endptr, int base);

long long strtoll(const char *restrict str, char **restrict endptr,
int base);

long atol(const char *str);

long long atoll(const char *str);

int atoi(const char *str);

char *lltostr(long long value, char *endptr);

char *ulltostr(unsigned long long value, char *endptr);

DESCRIPTION

strtol() and strtoll()
The strtol() function converts the initial portion of the string
pointed to by str to a type long int representation.

The strtoll() function converts the initial portion of the string
pointed to by str to a type long long representation.

Both functions first decompose the input string into three parts: an
initial, possibly empty, sequence of white-space characters (as
specified by isspace(3C)); a subject sequence interpreted as an
integer represented in some radix determined by the value of base;
and a final string of one or more unrecognized characters, including
the terminating null byte of the input string. They then attempt to
convert the subject sequence to an integer and return the result.

If the value of base is 0, the expected form of the subject sequence
is that of a decimal constant, octal constant or hexadecimal
constant, any of which may be preceded by a + or - sign. A decimal
constant begins with a non-zero digit, and consists of a sequence of
decimal digits. An octal constant consists of the prefix 0 optionally
followed by a sequence of the digits 0 to 7 only. A hexadecimal
constant consists of the prefix 0x or 0X followed by a sequence of
the decimal digits and letters a (or A) to f (or F) with values 10 to
15 respectively.

If the value of base is between 2 and 36, the expected form of the
subject sequence is a sequence of letters and digits representing an
integer with the radix specified by base, optionally preceded by a +
or - sign. The letters from a (or A) to z (or Z) inclusive are
ascribed the values 10 to 35; only letters whose ascribed values are
less than that of base are permitted. If the value of base is 16, the
characters 0x or 0X may optionally precede the sequence of letters
and digits, following the sign if present.

The subject sequence is defined as the longest initial subsequence of
the input string, starting with the first non-white-space character,
that is of the expected form. The subject sequence contains no
characters if the input string is empty or consists entirely of
white-space characters, or if the first non-white-space character is
other than a sign or a permissible letter or digit.

If the subject sequence has the expected form and the value of base
is 0, the sequence of characters starting with the first digit is
interpreted as an integer constant. If the subject sequence has the
expected form and the value of base is between 2 and 36, it is used
as the base for conversion, ascribing to each letter its value as
given above. If the subject sequence begins with a minus sign, the
value resulting from the conversion is negated. A pointer to the
final string is stored in the object pointed to by endptr, provided
that endptr is not a null pointer.

In other than the POSIX locale, additional implementation-dependent
subject sequence forms may be accepted.

If the subject sequence is empty or does not have the expected form,
no conversion is performed; the value of str is stored in the object
pointed to by endptr, provided that endptr is not a null pointer.

atol(), atoll() and atoi()
Except for behavior on error, atol() is equivalent to: strtol(str,
(char **)NULL, 10).

Except for behavior on error, atoll() is equivalent to: strtoll(str,
(char **)NULL, 10).

Except for behavior on error, atoi() is equivalent to: (int)
strtol(str, (char **)NULL, 10).

If the value cannot be represented, the behavior is undefined.

lltostr() and ulltostr()
The lltostr() function returns a pointer to the string represented by
the long long value. The endptr argument is assumed to point to the
byte following a storage area into which the decimal representation
of value is to be placed as a string. The lltostr() function
converts value to decimal and produces the string, and returns a
pointer to the beginning of the string. No leading zeros are
produced, and no terminating null is produced. The low-order digit of
the result always occupies memory position endptr-1. The behavior of
lltostr() is undefined if value is negative. A single zero digit is
produced if value is 0.

The ulltostr() function is similar to lltostr() except that value is
an unsigned long long.

RETURN VALUES

Upon successful completion, strtol(), strtoll(), atol(), atoll(), and
atoi() return the converted value, if any. If no conversion could be
performed, strtol() and strtoll() return 0 and errno may be set to
EINVAL.

If the correct value is outside the range of representable values,
strtol() returns LONG_MAX or LONG_MIN and strtoll() returns LLONG_MAX
or LLONG_MIN (according to the sign of the value), and errno is set
to ERANGE.

Upon successful completion, lltostr() and ulltostr() return a pointer
to the converted string.

ERRORS

The strtol() and strtoll() functions will fail if:

ERANGE
The value to be returned is not representable. The strtol()
and strtoll() functions may fail if:

EINVAL
The value of base is not supported.

USAGE

Because 0, LONG_MIN, LONG_MAX, LLONG_MIN, and LLONG_MAX are returned
on error and are also valid returns on success, an application
wishing to check for error situations should set errno to 0, call the
function, then check errno and if it is non-zero, assume an error has
occurred.

The strtol() function no longer accepts values greater than LONG_MAX
or LLONG_MAX as valid input. Use strtoul(3C) instead.

Calls to atoi() and atol() might be faster than corresponding calls
to strtol(), and calls to atoll() might be faster than corresponding
calls to strtoll(). However, applications should not use the atoi(),
atol(), or atoll() functions unless they know the value represented
by the argument will be in range for the corresponding result type.

ATTRIBUTES