david@utzoo.UUCP (David Trueman) (03/15/84)
We are now running the System 5 shell with some local modifications:
echo(1) has been built in, the "bye" command has been added and various
incompatabilities with V7 have been fixed.
There are a number of changes with respect to the V7 shell:
- test(1) is built in and has several new options
- the "cd" command will search a number of directories specified
by the CDPATH environment variable
- the # character begins a comment; the rest of the line is ignored
- "here documents" beginning with <<- have leading tabs stripped
- parameter substitutions using curly braces and with a colon after
the parameter name treat a null parameter the same as unset
- '--' indicates the end of shell options on the command line or
when using the "set" command
- use of '+' inoptions or with "set" turns the option(s) off
- a login shell reads from /etc/profile before $HOME/.profile
- the "shift" command takes a number argument
- in filename matching, if the first character of a character class
(indicated by []) is '!', then the sense of the match is reversed
- process creation is done more carefully: repeated attempts are made
to fork at ever-increasing intervals up to a limit, and then it quits
- signal 11 (segmentation violation) cannot be trapped
- only signals 2, 3, 14, 15 are caught by default (in V7 all signals
were caught, even if the action taken was to die immediately)
In general, a number of bugs have been fixed, and more care is taken to
maintain the correct exit code.
--
David Trueman @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!david