strtol, strtoll, atol, atoll, atoi, lltostr, ulltostr -
string conversion routines
long strtol(const char *str, char **endptr, int base);
long long strtoll(const char *str, char **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);
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 deter-
mined 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
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 charac-
ters 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 result-
ing from the conversion is negated. A pointer to the final
string is stored in the object pointed to by endptr, pro-
vided 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).
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.
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.
The strtol() and strtoll() functions will fail if:
The value to be returned is not representable. The
strtol() and strtoll() functions may fail if:
The value of base is not supported.
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)
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | MT-Safe |
isalpha(3C), isspace(3C), scanf(3C), strtod(3C),
Man(1) output converted with