strtold(3) [netbsd man page]
STRTOD(3) BSD Library Functions Manual STRTOD(3) NAME
strtod, strtof, strtold -- convert ASCII string to double, float, or long double LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <stdlib.h> double strtod(const char * restrict nptr, char ** restrict endptr); float strtof(const char * restrict nptr, char ** restrict endptr); long double strtold(const char * restrict nptr, char ** restrict endptr); DESCRIPTION
The strtod() function converts the initial portion of the string pointed to by nptr to double representation. The strtof() function converts the initial portion of the string pointed to by nptr to float representation. The strtold() function converts the initial portion of the string pointed to by nptr to long double representation. 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 followed 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 skipped. RETURN VALUES
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 supported, else remains unrecognized (i.e., VAX). If endptr is not NULL, a pointer to the character after the last character used in the conversion 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 location 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 errno. ERRORS
[ERANGE] Overflow or underflow occurred. SEE ALSO
atof(3), atoi(3), atol(3), math(3), strtol(3), strtoul(3) STANDARDS
The strtod() function conforms to ANSI X3.159-1989 (``ANSI C89''). The strtof() and strtold() functions conform to ISO/IEC 9899:1999 (``ISO C99''). HISTORY
The strtof() and strtold() functions appeared in NetBSD 4.0. BSD
March 12, 2006 BSD
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STRTOD(3) Linux Programmer's Manual STRTOD(3) NAME
strtod, strtof, strtold - convert ASCII string to floating-point number SYNOPSIS
#include <stdlib.h> double strtod(const char *nptr, char **endptr); float strtof(const char *nptr, char **endptr); long double strtold(const char *nptr, char **endptr); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): strtof(), strtold(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99 DESCRIPTION
The strtod(), strtof(), and strtold() functions convert the initial portion of the string pointed to by nptr to double, float, and long double representation, respectively. The expected form of the (initial portion of the) string is optional leading white space as recognized by isspace(3), an optional plus ('+') or minus sign ('-') and then either (i) a decimal number, or (ii) a hexadecimal number, or (iii) an infinity, or (iv) a NAN (not-a- number). A decimal number consists of a nonempty sequence of decimal digits possibly containing a radix character (decimal point, locale-dependent, usually '.'), optionally followed by a decimal exponent. A decimal exponent consists of an 'E' or 'e', followed by an optional plus or minus sign, followed by a nonempty sequence of decimal digits, and indicates multiplication by a power of 10. A hexadecimal number consists of a "0x" or "0X" followed by a nonempty sequence of hexadecimal digits possibly containing a radix charac- ter, optionally followed by a binary exponent. A binary exponent consists of a 'P' or 'p', followed by an optional plus or minus sign, followed by a nonempty sequence of decimal digits, and indicates multiplication by a power of 2. At least one of radix character and binary exponent must be present. An infinity is either "INF" or "INFINITY", disregarding case. A NAN is "NAN" (disregarding case) optionally followed by '(', a sequence of characters, followed by ')'. The character string specifies in an implementation-dependent way the type of NAN. RETURN VALUE
These functions return the converted value, if any. If endptr is not NULL, a pointer to the character after the last character used in the conversion 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 location referenced by endptr. If the correct value would cause overflow, plus or minus HUGE_VAL (HUGE_VALF, HUGE_VALL) is returned (according to the 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 errno. ERRORS
ERANGE Overflow or underflow occurred. CONFORMING TO
C89 describes strtod(), C99 describes the other two functions. NOTES
Since 0 can legitimately be returned on both success and failure, the calling program should set errno to 0 before the call, and then determine if an error occurred by checking whether errno has a nonzero value after the call. EXAMPLE
See the example on the strtol(3) manual page; the use of the functions described in this manual page is similar. SEE ALSO
atof(3), atoi(3), atol(3), strtol(3), strtoul(3) COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2007-07-26 STRTOD(3)