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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: How to use a temporary file in a portable way
Date: Fri, 10 Apr 2015 08:29:49 -0700
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Richard Damon <Richard@Damon-Family.org> writes:
> On 4/9/15 1:22 AM, pozz wrote:
>> How to choose the temporary file name?  How to face the situation when
>> the temporary file name already exist?
>
> Call tmpnam(). From the standard:
> The tmpnam function generates a string that is a valid file name and
> that is not the same as the name of an existing file.

tmpnam() has potential problems.  The Linux man page says:

    Although tmpnam() generates names that are difficult to guess,
    it is nevertheless possible that between the time that tmpnam()
    returns a pathname, and the time that the program opens it,
    another program might create that pathname using open(2), or
    create it as a symbolic link.  This can lead to security holes.
    To avoid such possibilities, use the open(2) O_EXCL flag to
    open the pathname.  Or better yet, use mkstemp(3) or tmpfile(3).

    ...

    BUGS

       Never use this function.  Use mkstemp(3) or tmpfile(3) instead.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"