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While the likelihood of access() returning a false negative is lower than that of fopen(), on file systems where the program does not have sufficient permissions in the directory to view the file, access() may return -1 even when the file exists. In such cases, rename() will also likely fail since the program does not have adequate permissions inside the directory.

Compliant Solution (Windows)

On Windows, [{{_access_s()}}|http://msdn.microsoft.com/en-us/library/a2xs1dts(VS.80).aspx] allows one to check for the existence of a file \[[MSDN|AA. C References#MSDN]\].

char const *old = /* ... */;
char const *new = /* ... */;

if (_access_s(new,0) != 0) {
  if (rename(old, new) != 0) {
    /* Handle Error */
  }
} else {
  /* Handle Error */
}

This _access_s() example shares many of the same problems as the POSIX access() example above.

Risk Assessment

Calling rename() has implementation-defined behavior when the new file name refers to an existing file. Incorrect use of rename() can result in a file being unexpectedly overwritten or other unexpected behavior.

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\[[ISO/IEC 9899:1999|AA. C References#ISO/IEC 9899-1999]\] Section 7.9.4.2, "The {{rename}} function"
\[[MSDN|AA. C References#MSDN]\] [{{_access_s, _waccess_s}}|http://msdn.microsoft.com/en-us/library/a2xs1dts(VS.80).aspx]
\[[Open Group 04|AA. C References#Open Group 04]\] [{{access()}}|http://www.opengroup.org/onlinepubs/009695399/functions/access.html]

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