ATOF
Section: POSIX Programmer's Manual (3P)
Updated: 2017
Page Index
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.
NAME
atof
--- convert a string to a double-precision number
SYNOPSIS
#include <stdlib.h>
double atof(const char *str);
DESCRIPTION
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.
SEE ALSO
strtod()
The Base Definitions volume of POSIX.1-2017,
<stdlib.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .