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This code example is noncompliant because any existing destination file is removed by rename().:
| Code Block | ||||
|---|---|---|---|---|
| ||||
const char *src_file = /* ... */;
const char *dest_file = /* ... */;
if (rename(src_file, dest_file) != 0) {
/* Handle Error */
}
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If the programmer's intent is not to remove an existing destination file, the POSIX access() function can be used to check for the existence of a file [Open Group 2004]. This compliant solution renames the source file only if the destination file does not exist.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
const char *src_file = /* ... */;
const char *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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If the intent of the programmer is to remove the file referenced by dest_file if it exists prior to calling rename(), this code example is noncompliant on Windows platforms because rename() will fail.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
const char *src_file = /* ... */;
const char *dest_file = /* ... */;
if (rename(src_file, dest_file) != 0) {
/* Handle error */
}
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On Windows systems, it is necessary to explicitly remove the destination file before calling rename() if you want the file to be overwritten and the rename() operation to succeed.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
const char *src_file = /* ... */;
const char *dest_file = /* ... */;
if (_access_s(dest_file, 0) == 0) {
if (remove(dest_file) != 0) {
/* Handle error condition */
}
}
if (rename(src_file, dest_file) != 0) {
/* Handle error condition */
}
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This code contains unavoidable race conditions between the calls to _access_s(), remove(), and rename() and can consequently be safely executed only within a secure directory. (See FIO15-C. Ensure that file operations are performed in a secure directory.) Another option would be to use the MoveFileEx API, and pass in the MOVEFILE_REPLACE_EXISTING flag.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
const char *src_file = /* ... */;
const char *dest_file = /* ... */;
if (!MoveFileEx(src_file, dest_file, MOVEFILE_REPLACE_EXISTING)) {
/* Handle error condition */
}
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On POSIX systems, if the destination file exists prior to calling rename(), the file is automatically removed.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
const char *src_file = /* ... */;
const char *dest_file = /* ... */;
if (rename(src_file, dest_file) != 0) {
/* Handle error condition */
}
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This compliant solution ensures that any destination file is portably removed.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
const char *src_file = /* ... */;
const char *dest_file = /* ... */;
(void)remove(dest_file);
if (rename(src_file, dest_file) != 0) {
/* Handle error condition */
}
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This compliant solution renames the source file only if the destination file does not exist.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
const char *src_file = /* ... */;
const char *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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