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New files are automatically entered into the file directory as permanent files as soon as they are “opened”. Subsequent “closing” of a file does not automatically cause its deletion. As was seen at line 7352, deletion will occur when the field “i_nlink” of the core “inode” entry is zero. This field is set to one initially by “maknode” (7464) when the file is first created. It may be incremented by the system call “link” (5941) and decremented by the system call “unlink” (3529).
Programs which create temporary “work files” should remove these files before terminating, by executing an “unlink” system call. Note that the “unlink” call does not of itself remove the file. This can only happen when the reference count (“i_count”) is about to be decremented to zero (7350, 7362).
To minimise the problems associated with “temporary” files which survive program or system crashes, programmers should observe the conventions that:
temporary files should be “unlinked” immediately after they are opened;
temporary files should always be placed in the “tmp” directory. Unique file names can be generated by incorporating the process’s identifying number into the file name (See “getpid” (3480)).
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