ATOF(2) ATOF(2)
NAME
atof, atoi, atol, charstod, strtod, strtol, strtoul -
convert text to numbers
SYNOPSIS
double atof(char *nptr)
int atoi(char *nptr)
long atol(char *nptr)
double charstod(int (*f)(void *), void *a)
double strtod(char *nptr, char **rptr)
long strtol(char *nptr, char **rptr, int base)
ulong strtoul(char *nptr, char **rptr, int base)
DESCRIPTION
Atof, atoi, and atol convert a string pointed to by nptr to
floating, integer, and long integer representation respec-
tively. The first unrecognized character ends the string.
Atof recognizes an optional string of tabs and spaces, then
an optional sign, then a string of digits optionally con-
taining a decimal point, then an optional `e' or `E' fol-
lowed by an optionally signed integer.
Atoi and atol recognize an optional string of tabs and
spaces, then an optional sign, then a string of decimal dig-
its.
Strtod, strtol, and strtoul, behave similarly to atof, and
atol and, if rptr is not zero, set *rptr to point to the
input character immediately after the string converted.
Strtol and strtoul interpret the digit string in the speci-
fied base, from 2 to 36, each digit being less than the
base. Digits with value over 9 are represented by letters,
a-z or A-Z. If base is 0, the input is interpreted as an
integral constant in the style of C (with no suffixed type
indicators): numbers are octal if they begin with `0', hex-
adecimal if they begin with `0x' or `0X', otherwise decimal.
Strtoul does not recognize signs.
Charstod interprets floating point numbers like atof, but it
gets successive characters by calling (*f)(a). The last
call to f terminates the scan, so it must have returned a
character that is not a legal continuation of a number.
Page 1 Plan 9 (printed 11/18/24)
ATOF(2) ATOF(2)
Therefore, it may be necessary to back up the input stream
one character after calling charstod.
SEE ALSO
fscanf(2)
DIAGNOSTICS
Zero is returned if the beginning of the input string is not
interpretable as a number; even in this case, rptr will be
updated.
BUGS
Atoi and atol accept octal and hexadecimal numbers in the
style of C, contrary to the ANSI specification.
Page 2 Plan 9 (printed 11/18/24)