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There are access permissions for UNIX system files to control who may read, write, or execute such a file. These access permissions may only be set by the owner of the file or by a process with the appropriate privilege. The permissions of the directory in which the file resides can also affect the ultimate disposition of a file. Note that if the directory permissions allow anyone to write in it, then files within the directory may be removed, even if those files do not have read, write or execute permission for that user. Any information that is worth protecting, is worth protecting properly. If your application warrants the use of record locking, make sure that the permissions on your files and directories are set properly. A record lock, even a mandatory record lock, will only protect the portions of the files that are locked. Other parts of these files might be corrupted if proper precautions are not taken.
Only a known set of programs and/or administrators should be able to read or write a data base. This can be done easily by setting the set-group-ID bit of the data base accessing programs (see chmod(C)). The files can then be accessed by a known set of programs that obey the record locking protocol. An example of such file protection, although record locking is not used, is the mail command. In that command only the particular user and the mail command can read and write in the unread mail files.