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Name

Synopsis

#include <stdlib.h>

double strtod(const char *nptr, char **endptr);

double atof(const char *nptr);

MT-Level

MT-Safe

Description

strtod() recognizes an optional string of ‘‘white-space’’ characters (as defined by isspace() in ctype(3C) ), then an optional sign, then a string of digits optionally containing a decimal point character, then an optional exponent part including e or E followed by an optional sign, followed by an integer. The decimal point character is defined by the program’s locale (category LC_NUMERIC ). In the "C" locale, or in a locale where the decimal point character is not defined, the decimal point character defaults to a period (.).

If the value of endptr is not (char **)NULL , a pointer to the character terminating the scan is returned in the location pointed to by endptr. If no number can be formed, *endptr is set to nptr, and zero is returned.

atof(nptr) is equivalent to:
   strtod(nptr, (char **)NULL ).

LC_NUMERIC

Determines how strtod and atof handle numeric formats. In the "C" locale, numeric handling follows the U.S. rules.

Return Values

If the correct value would cause overflow, ±HUGE is returned (according to the sign of the value), and errno is set to ERANGE .

If the correct value would cause underflow, 0 is returned and errno is set to ERANGE .

When the -Xc or -Xa compilation options are used, HUGE_VAL is returned instead of HUGE .

If nptr is NaN, then atof() returns NaN.

Files

/usr/lib/locale/locale/LC_NUMERIC/numeric

LC_NUMERIC database for locale

See Also

Table of Contents

• Name
• Synopsis
• MT-Level
• Description
• Return Values
• Files
• See Also