Pid

Shell Programming and Scripting
1

How can I put the process id of ,for example, the following script to the pid file? Maybe $$ must be defined in some place?

daemon(){
        while true;
        do
                if [ -r "${FILE}" ]
                then
                        echo "`date +"%H:%M:%S"`" >> $FILE
                        sleep 3;
                fi
        done
}
daemon >/dev/null 2>&1 &
2

FYI: $$ is the pid of the current process, so:

echo "`date +"%H:%M:%S"` $$" >> $FILE

does write the pid to $FILE, but it is a child process because the & runs the function in the background.

3

Good point... You may be able to 'source' the command by prepending a period[SPACE] so it runs in the same process/shell.

Untested but worth a shot:

. echo "`date +"%H:%M:%S"` $$" >> $FILE
4

I think the "daemon" is meant to run by itself in a child process. It doesn't do much.
Maybe they use to track usage of the script that runs it...

5

This example script works perfect only in following configuration:

daemon(){
        echo $$ > ${PF}
        while true; 
        do 
                if [ -r "${FILE}" ]
                then 
                        echo "`date +"%H:%M:%S"`" >> $FILE
                        sleep 3;
                fi
        done
}

#MAIN
case $1 in
        -daemon)
                daemon
                ;;
        *)
                $0 -daemon &
                ;;
esac
exit 0