mirror of https://github.com/mkerrisk/man-pages
atoi.3: Explain disadvantages of atoi()
I believe new users should be discouraged from using atoi() and that its disadvantages should be explained. I added the information that 0 is returned on error - although C standard and POSIX say that "If the value of the result cannot be represented, the behavior is undefined." there are some interpretations that 0 has to be returned https://stackoverflow.com/questions/38393162/what-can-i-assume-about-the-behaviour-of-atoi-on-error and this is also what happens in practice with glibc, musl and uClibc. Signed-off-by: Arkadiusz Drabczyk <arkadiusz@drabczyk.org> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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man3/atoi.3
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man3/atoi.3
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@ -81,7 +81,18 @@ functions behave the same as
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except that they convert the initial portion of the
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except that they convert the initial portion of the
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string to their return type of \fIlong\fP or \fIlong long\fP.
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string to their return type of \fIlong\fP or \fIlong long\fP.
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.SH RETURN VALUE
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.SH RETURN VALUE
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The converted value.
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The converted value or 0 on error.
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.SH BUGS
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.I errno
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is not set on error so there is no way to distinguish between 0 as an
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error and as the converted value.
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No checks for overflow or underflow are done.
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Only input in decimal base can be converted.
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It's recommended to use
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.BR strtol ()
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and
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.BR strtoul ()
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family of functions in new programs.
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.SH ATTRIBUTES
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.BR attributes (7).
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