Standard Library

sysafe

DOCUMENT sysafe, "command line"
      or system, "command line"
  pass the command line to a UNIX sh (Bourne) shell for execution.
  This requires a fork() system call, which in turn makes a copy of
  the yorick executable in virtual memory before replacing that copy
  with the sh shell.  If yorick has grown to enormous size, the copy
  can bring your machine to its knees or kill it.  If you include
  sysafe.i before yorick grows (before you start the calculation that
  requires the large data arrays), a pipe is opened to an sh which
  remains running, and the original system command is replaced by
  sysafe.  Future system commands will be piped to the already
  running sh, so no dangerous copy operation is required.

  There are four problems with this approach:
    (1) You can't run interactive programs with sysafe, because the
        stdin is from the pipe (sysafe_pipe) instead of the keyboard.
        Attempting to do so may lock up yorick.
    (2) Since the command runs asynchronously now, yorick can't wait
        until it completes, and yorick's prompt will often precede
        the output from the command, unlike using the default system
        function.
    (3) Some typographical errors in commands may kill the sh; since
        you don't start a new one each time, the system command will
        stop working.
    (4) The shorthand $ syntax still uses the dangerous system call;
        you need to call system as an ordinary function for sysafe
        to protect you.

SEE ALSO: system_orig