NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/5410

Internet Message Format | 1996-08-05 | 2.5 KB

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From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: How to tell if a file exists in C
Date: Thu, 08 Feb 96 15:11:14 GMT
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References: <4eqkj6$[e-mail]> <[e-mail]>
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In article <[e-mail]>
           [e-mail] "jan-henrik haukeland" writes:

>Lawrence Kirby writes:
>
> : [e-mail] "jan-henrik haukeland" writes:
> :
> : >Use the stat function, e.g.:
> : >
> : >int fexist(char * filename)
>
><snip>
>
> : This function returns 3 distinct values. As such it does not return a
> : voolean-like quantity. Therefore it is highly misleading to label two of
> : those return values as TRUE and FALSE - you should find some more
> : appropriate names.
>
>Should I ?

Definitely.

>Lets see, either the file exist or it don't - Yes.

No. In the general case there are 4 possibilities:

1. The file is determined to exist.
2. The file is determined not to exist
3. it isn't possible to tell (e.g. inadequate permissions on a path element)
4. an error occurred

>Normal usage
>of this function would be, something like:
>
>        if ( ! fexist(filename)) {
>          /* Do stuff */
>        }
>
>See, either it exist or it don't - and thats Boolean.

! tests for zero or nonzero - it does *not* take a boolean operand although
it generates a boolean-like result. x==5 also generates a boolean-like result
but doesn't imply that x is boolean.

>But as a special
>"fyzzy logic" service, it will distinguish between TRUE, because even if it
>is TRUE that it exist, it's maybe not so true as You would like it to be,
>because it's NOT_A_REGULAR_FILE (i.e. a dir. a /dev ..). It is then
>possible to test for this. Beside did I say it was a boolean function, I
>think not.

You indicated that by using TRUE and FALSE as return values. They carry
a strong implication that the quantity is boolean-like hence they are
the only possible values. Since that is not the case here you are
misleading the reader. It is simply better to use names that describe the
meaning of the values more clearly.

--
-----------------------------------------
Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
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