On Fri, Aug 20, 2010 at 6:36 PM, Paul E Condon <pecon...@mesanetworks.net> wrote: > I'm debugging some bash scripts and reading the scripts that come as > part of Squeeze installation. I find several places where there are > statements the set a value from variable PS1, BUT all of them seem > to be in scripts that only get executed if PS1 is already non-empty. > i.e. they are after a statement > [ -z "$PS1" ] && return > which, I think, executes return if PS1 is empty. > > A related question: > The comment just before the above line of code is: > "# If not running interactively, don't do anything" > > For me, the implication of this comment is that a non-empty PS1 IS > the defining characteristic of 'running interactively', but I would > have thought 'interactive' should be characterized by having a tty > attached to sysin and sysout for communication to a 'user'. > > I can imagine that a non-empty PS1 is used as an indicator, in which > case whatever code that actually sets up the tty also sets PS1 to > some minimal non-empty value like a single space or a dot, but is > this actually the way it works, and where is it? > > Where can I read about these issues?
>From "man bash" (not being obnoxious) An interactive shell is one started without non-option arguments and without the -c option whose standard input and error are both connected to terminals (as determined by isatty(3)), or one started with the -i option. PS1 is set and $- includes i if bash is interactive, allowing a shell script or a startup file to test this state. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/aanlktiknyc8fqxfsgq7ttwhovplzlhn+osmsogx1s...@mail.gmail.com
