Page History

The next code sample attempts to remedy the problem by using the POSIX {{open()}}, defined in the Open Group Base Specifications Issue 6 \[[Open Group 04|AA. C References#Open Group 04]\] function, and providing a mechanism to indicate whether an existing file has been opened for writing or a new file has been created \[[Open Group 04|AA. C References#Open Group 04]\]. If the {{O_CREAT}} and {{O_EXCL}} flags are used together, the {{open()}} function fails when the file specified by {{file_name}} already exists. To prevent an existing file from being opened and truncated, include the flags {{O_CREAT}} and {{O_EXCL}} when calling {{open()}}.

Moreover, the {{open()}} function as specified by the Open Group Base Specifications Issue 6 \[[Open Group 04|AA. C References#Open Group 04]\] does not include support for shared or exclusive locks. However, BSD systems support two additional flags that allow you to

 obtain these locks: