ATOF(3P)

💖 PROLOG 💖

okay so first things first, bestie: this manual page is part of the POSIX Programmer's Manual. heads up tho — the Linux implementation of this interface may differ (so go consult the corresponding Linux manual page for the deets on Linux behavior), or the interface may not even be implemented on Linux at all. 🙈

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✨ NAME ✨

atof — convert a string to a double-precision number 💅

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🌸 SYNOPSIS 🌸

#include <stdlib.h>

double atof(const char *str);

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🦋 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, fr — this volume of POSIX.1‐2017 defers to the ISO C standard, no cap.

The call atof(str) shall be equivalent to:

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

except that the handling of errors may differ. 👀

⚠️ real talk: if the value cannot be represented, the behavior is undefined. like, undefined undefined. don't test it. 💀

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🎀 RETURN VALUE 🎀

The atof() function shall return the converted value if the value can be represented. that's it, that's the whole vibe. ✨

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💅 ERRORS 💅

No errors are defined. iconically unbothered, honestly. 😌

The following sections are informative.

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🍓 EXAMPLES 🍓

None. (yes literally none, the page said what it said 🙈)

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👑 APPLICATION USAGE 👑

Okay so here's the tea: the atof() function is subsumed by strtod() but is retained because it is used extensively in existing code. legacy code said "not me being everywhere" and honestly? valid.

But listen — if the number is not known to be in range, strtod() should be used, because atof() is not required to perform any error checking. so if you don't know your input is safe, use the other one. periodt. 🔥

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🌈 RATIONALE 🌈

None.

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🧚 FUTURE DIRECTIONS 🧚

None.

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⭐ SEE ALSO ⭐

• strtod()
• The Base Definitions volume of POSIX.1‐2017, <stdlib.h>

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💜 COPYRIGHT 💜

okay this is the part where we all sit up straight, because it's the legal bit and it matters:

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 .

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and that's the whole page, bestie 🫶 this one came from the IEEE/The Open Group, dated 2017, and it lives in the ATOF(3P) slot in the manual — mwah, take care of her 💖