ATOF(2)
NAME
atof, atoi, atol, charstod, strtod, strtol, strtoul − convert text to numbers
SYNOPSIS
doubleatof(char ∗nptr)
intatoi(char ∗nptr)
longatol(char ∗nptr)
doublecharstod(int (∗f)(void ∗), void ∗a)
doublestrtod(char ∗nptr, char ∗∗rptr)
longstrtol(char ∗nptr, char ∗∗rptr, int base)
ulongstrtoul(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 respectively. The first unrecognized character ends the string. Leading C escapes are understood, as in strtol with base zero.
Atof recognizes an optional string of tabs and spaces, then an optional sign, then a string of digits optionally containing a decimal point, then an optional e or E followed 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 digits.
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 specified 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, hexadecimal 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. Therefore, it may be necessary to back up the input stream one character after calling charstod.
SEE ALSO
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.
Plan 9 — January 03, 1993