question-- Bourne (and C) SHELL

[Steven Augart]

   From: Arturo Perez <arturo%humming.uucp at BRL.ARPA>
   Date: 14 Aug 86 14:12:45 GMT

   In the csh you can do something like

   ls foo
   if (! $status) then
      echo "foo exists"
   endif

(parenthetical note: "ls" will return status 0 whether or not it can
find foo.  The example is faulty).

   The  key  thing  here  is  the  ability  to NOT the value of status. How is
   this similar thing done in Bourne shell.

Can't be done directly in the Bourne shell, since the Bourne shell
simply doesn't have C-shell style expressions; they are handled
separately by the "test" and "expr" programs.  Since the bourne shell
doesn't have expressions, it also doesn't have an internal NOT
operator.

However, you can do this simple workaround (or you could if "ls foo"
returned 0 status to indicate that it found "foo" and nonzero status
to indicate that it hadn't found "foo"):

    if ls foo
    then
	    ;
    else
	    echo "foo not found"
    endif


Steven Augart
MIT Laboratory for Computer Science
swa at xx.lcs.mit.edu, swa at xx.ARPA