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If the desired behavior is to ensure that any file referenced by dest_file the destination file is not erased or overwritten, POSIX programmers must implement additional safeguards.

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This code example is non-compliant because if dest_the destination file exists it is removed by rename().

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Compliant Solution (POSIX)

If the programmer's intent of the programmer is to not remove theany fileexisting referenced by {{dest_file}} if it exists prior to calling {{rename()}}destination file, the POSIX {{access()}} function can be used to check for the existence of a file explicitly \[[Open Group 04|AA. C References#Open Group 04]\]. This compliant solution only renames the file referenced by {{src_file}}source file if the file referenced by {{dest_file}}destination file does not exist.

char const *src_file = /* ... */;
char const *dest_file = /* ... */;

if (access(dest_file, F_OK) != 0) {
  if (rename(src_file, dest_file) != 0) {
    /* Handle error condition */
  }
} 
else {
  /* Handle file-exists condition */
}

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Consequently, it is unnecessary to explicitly check for the existence of the file referenced by dest_destination file before calling rename().

char const *src_file = /* ... */;
char const *dest_file = /* ... */;
if (rename(src_file, dest_file) != 0) {
  /* Handle Error */
}

Erase Existing

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Destination File

If the desired behavior is to ensure that any file referenced by dest_the destination file is erased by the rename() operation, Windows programmers must write additional code.

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On Windows systems, it is necessary to explicitly remove the file referenced by dest_destination file before calling rename(), if you want the file to be overwritten and the rename() operation to succeed.

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Compliant Solution (POSIX)

On POSIX systems, if the file referenced by dest_destination file exists prior to calling rename(), the file is automatically removed.

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This compliant solution ensures that any file referenced by dest_destination file is portably removed.

char const *src_file = /* ... */;
char const *dest_file = /* ... */;

(void)remove(dest_file);

if (rename(src_file, dest_file) != 0) {
  /* Handle error condition */
}

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This compliant solution only renames the file referenced by src_source file if the file referenced by dest_destination file does not exist.

char const *src_file = /* ... */;
char const *dest_file = /* ... */;

if (!file_exists(dest_file)) {
  if (rename(src_file, dest_file) != 0) {
    /* Handle error condition */
  }
} 
else {
  /* Handle file-exists condition */
}

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