On Sun, Jan 30, 2000 at 02:21:25PM +0100, Gustav Schaffter wrote:
| SoloCDM wrote:
| > How do I issue a command that will prevent two possible executed
| > instances of the same program?
|
| Short answer: You can't. (At least AFAIK :-)
| Long answer: You can. Almost.
| You may create a shell script (I believe) or a Perl script (I know) that
| will use flock to verify that it is running in one instance only. [...]
Flock doesn't always work over nfs. And there isn't always a handy
file to put a lock on anyway, depending.
But yes, you want a wrapper which uses an agreed-upon convention.
Then you never invoke the program directly, just the wrapper.
I do this for my mutt invocations, here's the wrapper:
#!/bin/sh
#
# Shortcut to threaded mailbox.
# - Cameron Simpson <[EMAIL PROTECTED]> 11oct99
#
box=`basename "$0"`
exec term -n "mutt $box" -e pushttylabel "mutt $box" lock "mail/$box" mutt -f
"$box"
Let's look at that one:
- this script is linked to the names "+attn", "+linux-misc", etc so
to read particular mailboxes I just type the command "+attn" etc
- "term" is just a script to open a new window (or not, if X
isn't active)
- "lock" is the core locking tool
its first argument is the name for the lock, "mail/+attn"
in this case if I'd typed "+attn"
its remaining arguments are a command to run once the lock
is obtained
it takes a few other options, like "-1" to say "if the lock's
taken don't bother running the command at all" which is handy
to ensure some service it up without starting multiple copies
So this script opens a new window, obtains a lock on the mailbox and
then runs mutt.
You can obtain lock from
http://www.zip.com.au/~cs/scripts/lock
You will want a lock directory; in the absense of other config it uses
$HOME/.locks
It requires my perl modules, from here:
http://www.zip.com.au/~cs/cs.tar.gz
There's a (quite) little writeup at:
http://www.zip.com.au/~cs/#scripts
Cheers,
--
Cameron Simpson, DoD#743 [EMAIL PROTECTED] http://www.zip.com.au/~cs/
When I grow up I want to be an idiot savant. I'm already halfway there...
- Kenneth, [EMAIL PROTECTED]
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