Skip to end of metadata
Go to start of metadata

You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 23 Next »

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 to test file existence potentially allowing a program to overwrite or access and unintended file.

Non-Compliant Example 1

In this example, a file name is supplied to fopen() to create and open for writing. However, there is no guaruntee that the file referenced by file_name does not exist prior to calling fopen(). This may cause an unintended file to be overwritten.

...
FILE * fptr = fopen(file_name, "w");
if (!fptr) {
  /* Handle Error */
}
...

Compliant Solution 1.

The open() function (Open Group 04c) provides a a way to test for file existence. 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.

...
int fd = open(file_name, O_CREAT | O_EXCL | O_WRONLY, new_file_mode);
if (fd == -1) {
  /* Handle Error */
}
...

References

  • No labels