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Top Forums Shell Programming and Scripting Running function or command concurrently in a bash script Post 302283515 by otheus on Tuesday 3rd of February 2009 12:04:50 PM
Old 02-03-2009
An external process cannot change a variable in your current process. So BREAK cannot get changed from anything in process or Tunnel.sh.

However, you can switch on the existence of a file, like this:
Code:
LOCK=/var/run/tunnel-keepalive.pid
echo $$ >LOCK

# start tunnel here

while [ -f $LOCK ]; do
   # Test to see if tunnel is still up, if not: start again
   sleep 5
done


Last edited by otheus; 02-04-2009 at 10:22 AM.. Reason: space between $$ >
 

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SHLOCK(1)						      General Commands Manual							 SHLOCK(1)

NAME
shlock - create lock files for use in shell scripts SYNOPSIS
shlock -p pid -f name [ -b ] [ -u ] [ -c ] DESCRIPTION
Shlock tries to create a lock file named name and write the process ID pid into it. If the file already exists, shlock will read the process ID from the file and test to see if the process is currently running. If the process exists, then the file will not be created. Shlock exits with a zero status if it was able to create the lock file, or non-zero if the file refers to currently-active process. OPTIONS
-b Process IDs are normally read and written in ASCII. If the ``-b'' flag is used, then they will be written as a binary int. For compatibility with other systems, the ``-u'' flag is accepted as a synonym for ``-b'' since binary locks are used by many UUCP pack- ages. -c If the ``-c'' flag is used, then shlock will not create a lock file, but will instead use the file to see if the lock is held by another program. If the lock is valid, the program will exit with a non-zero status; if the lock is not valid (i.e., invoking shlock without the flag would have succeeded), then the program will exit with a zero status. EXAMPLES
The following example shows how shlock would be used within a shell script: LOCK=/var/run/innd/LOCK.send trap 'rm -f ${LOCK} ; exit 1' 1 2 3 15 if shlock -p $$ -f ${LOCK} ; then # Do appropriate work else echo Locked by `cat ${LOCK}` fi HISTORY
Written by Rich $alz <rsalz@uunet.uu.net> after a description of HDB UUCP locking given by Peter Honeyman. This is revision 1.9, dated 1996/10/29. SHLOCK(1)
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