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Old 04-04-2005, 08:07 PM   #1
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shell script? : usage of $! with su -c option

I have a script that uses $! and su as follows (runs as root and java is in the path):


su javauser -c "java -jar $JAVA_USER_HOME/Server.jar > $SECURITY_SERVER_LOG 2>&1 &"
echo $! > $PID_FILE

Initialy I expected $! to contain the pid of the command passed to su, however, when the value is blank its clearly not what is happening.

So the question is, what can I do to still make sure that the java virtual machine runs under javauser as opposed to root, and still obtain the pid of the VM?

Thanks in advance,

Old 04-05-2005, 02:19 AM   #2
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I think that the problem is that the command doesn't run. Unless you don't have permission to write to a file in the /home/javauser/ directory. You might want to try it without the su -c part to see if it starts. Also saving the value of $? in a variable immediately after the the java command might supply some info. What does the $JAVA_USER_HOME/logfile indicate?

Also check that the javauser has a default shell entry in /etc/passwd.
Old 04-05-2005, 11:37 AM   #3
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I'll make sure and check the exit status before I cause any more trouble , but I don't expect it to indicate failure as the command does in fact run, and the log reflects normal operation of the program I expect to run. The only problem is that when I echo the PID to the pid file its empty. I modified the script so that it no longer uses su and the PID reappears, so it has to be something with the combination of $! and su. You'll have to forgive me for not posting the real script up to this point as I don't have it until I get to work, but when I do, I'll post the whole thing and hopefully something shakes out.


Last edited by DTParanoia; 04-05-2005 at 11:41 AM.
Old 04-05-2005, 06:58 PM   #4
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OK here is a trimmed down (trimmed to only the relevant sections to avoid post bloat) script that may or may not illustrate the isuue I am having. This is an init script to be placed into /etc/init.d and linked to by the various run levels, so it runs as root. When java is started I would very much like it to be run under a different user with lower privledge. I also need to retain the PID of the JVM, and this is where I am having trouble. I am doing it as follows, but I obviously need an alternative because its not working. I think its because there is a subshell involved and $! has no meaning to the shell in which I echo the value Fell free to review and correct me in any mistakes you see.

Just to summarize, the question is:

How do I run java as another user (other than root) and still retain the PID and write it (as root) to /var/run/ ?

# Set default values



# Define the server start commands.

# retain the pid of the server in order to kill
# it if a stop|restart is needed.

# if the log file does not exist then create it.
if [ -n "$SECURITY_SERVER_LOG" -a ! -e "$SECURITY_SERVER_LOG" ]; then

# if the existing log file does not exist or is not a regular file
# then send console output to /dev/null
if [ -n "$SECURITY_SERVER_LOG" -a ! -f "$SECURITY_SERVER_LOG" ]; then
echo "WARNING: ${SECURITY_SERVER_LOG} is not a valid log file."
echo "WARNING: The log will be sent to /dev/null"

# reset status of this service

case "$1" in
echo -n "Starting Service "


echo $! > $PID_FILE

rc_status -v


echo "Usage: $0 {start|stop|restart}"
exit 1

Last edited by DTParanoia; 04-05-2005 at 07:47 PM.


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