Running Scripts from cron but with controlling terminal (AIX)

Some Programs, like passwd(1) or, as in our (wu-wien.ac.at) case, kas, the kerberos authentication system, require that they are run from a controlling terminal. They try to open /dev/tty for writing and will refuse to work if this is impossible.

The solution is quit simple: acquire a controlling terminal beforehand using openpty(3) or forkpty(3). On AIX the semantics is a little bit different, it uses /dev/ptc as a svr4 - style "cloning" device.

In Stevens book "Advanced Programming in the UNIX Environment" there is an example Program in Chapter 19, "Pseudo Terminals". This program does not work on AIX, because

-) it uses the SVR4 /dev/ptmx instead of /dev/ptc (AIX).

-) it tries to push "ptem" "ldterm" "ttcompat" STREAMS modules onto the tty stream in the slave program. This does not seem to be necessary/possible anymore. I commented these lines out.

HOWTO do it

• Fetch the book examples from ftp://ftp.uu.net/published/books/stevens.advprog.tar.Z, uncompress an untar.

• patch the Directory using this patch:aix4_pty.patch. (It was created under FreeBSD with diff -urN)

  In the directory where you see the directory "apue", issue

  patch -p0 < aix4_pty.patch

• $ cd lib.svr4/
  $ make svr4
  $ cd ../pty/
  $ make pty
  

• Or download pty from here, flag it executable and start your script from cron like this:

  0 8 1 5 * pty -i myscript

• Read the source for commandline - switches that do not show up in the usage message and/or the Stevens Book.

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georg@graf.priv.at