atof3p
Convert a string to a double-precision number
Usage
#include <stdlib.h>
double atof(const char *str);
Prolog
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
Overview
The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1‐2017 defers to the ISO C standard.
The call atof(str) shall be equivalent to:
strtod(str,(char **)NULL),
except that the handling of errors may differ. If the value cannot be represented, the behavior is undefined.
Return value
The atof() function shall return the converted value if the value can be represented.
Errors
No errors are defined.
The following sections are informative.
Examples
None.
Application usage
The atof() function is subsumed by strtod() but is retained because it is used extensively in existing code. If the number is not known to be in range, strtod() should be used because atof() is not required to perform any error checking.
Rationale
None.
Future directions
None.