On 05/25/2013 11:42 AM, Derek Martin wrote:
One last point:
On Sat, May 25, 2013 at 09:32:02AM -0400, Greg Rundlett (freephile) wrote:
# we will use a prepared file 'users' whose contents are a list of users,
one user per line
while read USER
The variable $USER is set for you by the system when you log in, and
some things may depend on it (this is a very old Unix feature, and
I've forgotten which--most things should no longer do this, for the
reason I'm describing now). If you change the value of $USER, any
such things may break. Generally the convention is to use upper case
names for environment variables (i.e. things you want to have
persistence across sessions/processes/etc.), and shell scripts should
use lower case names for their variables to avoid unintended conflicts
like this.
Yes, using upper case for environment variables and lower case for local
variables is the long-time Unix/Linux convention. Shell scripts can use
both local as well as environment variables. I think your definition of
persistence is incorrect.
Environment variables persist within the process where they were
created, and any child process. However, a child process cannot affect
an environment variable in a parent or sibling process. There are a few
builtin environment variables. HOME and USER are two that are used
frequently.
--
Jerry Feldman <[email protected]>
Boston Linux and Unix
PGP key id:3BC1EB90
PGP Key fingerprint: 49E2 C52A FC5A A31F 8D66 C0AF 7CEA 30FC 3BC1 EB90
_______________________________________________
Discuss mailing list
[email protected]
http://lists.blu.org/mailman/listinfo/discuss
