The Earliest Unix Code: An Anniversary Source Code Release

Re:The Earliest Unix Code: An Anniversary Source Code Release by Pete_D on Thursday October 17, 2019 @07:09PM (#21287199)

> Maybe ‘pd’ is something like ‘prepare directory’, constructing the dd/dotdot entry.

I think this is on the right track - it looks like the write call is to the newly created .., with df being used to hold the file descriptor.

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Re:The Earliest Unix Code: An Anniversary Source Code Release by kazinator on Thursday October 17, 2019 @07:25PM (#21287284)

But the program appears to fail if dotdot can't be opened for reading, and it appears to scan through it doing reads first. Then it closes and does a creat, which is expected to succeed also. I'm suspecting that at this stage of development, open may have been used for reading and creat for writing (including to an existing file).

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Re:The Earliest Unix Code: An Anniversary Source Code Release by kps on Thursday October 17, 2019 @10:45PM (#21288220)

From TFS¹, creat() on an existing file truncates it (i.e. to length zero, as O_TRUNC), and only the superuser can do this to a directory. open() has read/write flag bits as now.

I am leaning toward Pete_D's ‘pack directory’ idea.

¹ https://github.com/DoctorWkt/pdp7-unix/blob/e94417092a2980e7...

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