Tasks

Write or fix a program. What grades it is the kernel's own record of what happened — the process table, the fd tables, the trace, the exit status and what was left behind — and not a reading of what you wrote.

• Read a file without leaving it openDescriptors · warm-up · 3 min

  Read the first eight bytes of /work/data and exit cleanly. When the process ends it must be holding nothing but the terminal — no file, no stray descriptor.

• Leave no zombiesProcesses · warm-up · 4 min

  Fork two children. Each should exit immediately. Your process must end with none of them left in the process table.

• The subprocess call that hangsDescriptors · real · 8 min

  The child writes a hundred kilobytes to a pipe and the parent waits for it to finish before reading. It never finishes. Fix it so both processes end, without changing what the child writes.

• Open it, do not ask about itDescriptors · real · 5 min

  Open /work/data for reading and handle the failure if it is not there. Do it without asking first whether it exists.

• Put a file on standard outputDescriptors · real · 6 min

  Write the word hello to /work/out — but the write must be to descriptor 1, exactly as a program that knows nothing about the file would do it.