The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


atof - convert a string to double-precision number


#include <stdlib.h>

double atof(const char *str);


The call atof(str) is equivalent to:

strtod(str,(char **)NULL),

except that the handling of errors may differ. If the value cannot be represented, the behaviour is undefined.


The atof() function returns the converted value if the value can be represented.


No errors are defined.




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.




strtod(), <stdlib.h>.


Derived from Issue 1 of the SVID.

UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
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