The ISO/IEC 9899-1999 C standard function fopen() is typically used to open an existing file , or create a new one. However, fopen() does not provide a way mechanism to determine if an existing file has been opened or a new file has been created. This may lead to a program overwriting or accessing an unintended file.
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In this example, a file name is supplied to fopen() to create and open for writing. However, there is no guaruntee guarantee that the file referenced by file_name does not exist prior to calling fopen(). This may cause an unintended file to be overwritten.
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FILE * fptr = fopen(file_name, "w");
if (!fptr) {
/* Handle Error */
}
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Compliant Solution 1.
The ISO/IEC 9899-1999 C standard does not provide a mechanism to determine if an existing file has been opened or a new file has been created. However, the open() function (as defined by Open Group 04c) provides a a way to test for file existence is available on many platforms and provides such a mechanism. If the O_CREAT and O_EXCL flags are used together, the open() function will fail if the file specified by file_name already exists.
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