STRTOD(3) BSD Library Functions Manual STRTOD(3)
strtod, strtof, strtold -- convert ASCII string to double, float, or long double
Standard C Library (libc, -lc)
strtod(const char * restrict nptr, char ** restrict endptr);
strtof(const char * restrict nptr, char ** restrict endptr);
strtold(const char * restrict nptr, char ** restrict endptr);
The strtod() function converts the initial portion of the string pointed to by nptr to
The strtof() function converts the initial portion of the string pointed to by nptr to float
The strtold() function converts the initial portion of the string pointed to by nptr to long
The expected form of the string is an optional plus ('+') or minus sign ('-') followed by
one of the following:
- a sequence of digits optionally containing a decimal-point character, optionally fol-
lowed by an exponent. An exponent consists of an 'E' or 'e', followed by an optional
plus or minus sign, followed by a sequence of digits.
- one of INF or INFINITY, ignoring case.
- one of NAN or NAN(n-char-sequence-opt), ignoring case. This implementation currently
does not interpret such a sequence.
Leading white-space characters in the string (as defined by the isspace(3) function) are
The strtod(), strtof(), and strtold() functions return the converted value, if any.
A character sequence INF or INFINITY is converted to infinity, if supported, else to the
largest finite floating-point number representable on the machine (i.e., VAX).
A character sequence NAN or NAN(n-char-sequence-opt) is converted to a quiet NaN, if sup-
ported, else remains unrecognized (i.e., VAX).
If endptr is not NULL, a pointer to the character after the last character used in the con-
version is stored in the location referenced by endptr.
If no conversion is performed, zero is returned and the value of nptr is stored in the loca-
tion referenced by endptr.
If the correct value would cause overflow, plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL
is returned (according to the return type and sign of the value), and ERANGE is stored in
errno. If the correct value would cause underflow, zero is returned and ERANGE is stored in
[ERANGE] Overflow or underflow occurred.
atof(3), atoi(3), atol(3), math(3), strtol(3), strtoul(3)
The strtod() function conforms to ANSI X3.159-1989 (``ANSI C89''). The strtof() and
strtold() functions conform to ISO/IEC 9899:1999 (``ISO C99'').
The strtof() and strtold() functions appeared in NetBSD 4.0.
BSD March 12, 2006 BSD