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Full Discussion: accessing variable from while loop
Top Forums Shell Programming and Scripting accessing variable from while loop Post 302627133 by neutronscott on Friday 20th of April 2012 08:35:18 AM
Old 04-20-2012
You will need to change the structure of the program to have a main loop to incorporate both timers, or use a sort of inter-process communication. One way would be to send a signal to the parent shell. Another would be a named fifo. Since we are just incrementing a number, we can use the simple signaling.

Code:
#!/bin/bash

#variable declared at start of script
x=0;

#a function that increments x by 1 every 10 seconds
incrementX() {
        local ppid=$1

        while true; do
                sleep 10
                kill -USR1 "$ppid"
        done
}

globalTimer() {
        while true; do
                sleep 1
                echo $x
        done
}

#increment x on signal from async timer
trap 'let x++' SIGUSR1
#kill children when we exit
trap 'kill 0' EXIT

#run both functions
incrementX $$ &
globalTimer

Last edited by neutronscott; 04-20-2012 at 09:40 AM.. Reason: kill children
 

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LEARN ABOUT X11R4

kill

KILL(1)                                                            User Commands                                                           KILL(1)

NAME

       kill - send a signal to a process

SYNOPSIS

       kill [options] <pid> [...]

DESCRIPTION

       The  default  signal  for kill is TERM.  Use -l or -L to list available signals.  Particularly useful signals include HUP, INT, KILL, STOP,
       CONT, and 0.  Alternate signals may be specified in three ways: -9, -SIGKILL or -KILL.  Negative PID values may be  used  to  choose  whole
       process  groups;  see  the  PGID  column  in ps command output.  A PID of -1 is special; it indicates all processes except the kill process
       itself and init.

OPTIONS

       <pid> [...]
              Send signal to every <pid> listed.

       -<signal>
       -s <signal>
       --signal <signal>
              Specify the signal to be sent.  The signal can be specified by using name or number.  The behavior of signals is explained  in  sig-
              nal(7) manual page.

       -l, --list [signal]
              List signal names.  This option has optional argument, which will convert signal number to signal name, or other way round.

       -L, --table
              List signal names in a nice table.

       NOTES  Your shell (command line interpreter) may have a built-in kill command.  You may need to run the command described here as /bin/kill
              to solve the conflict.

EXAMPLES

       kill -9 -1
              Kill all processes you can kill.

       kill -l 11
              Translate number 11 into a signal name.

       kill -L
              List the available signal choices in a nice table.

       kill 123 543 2341 3453
              Send the default signal, SIGTERM, to all those processes.

SEE ALSO

       kill(2), killall(1), nice(1), pkill(1), renice(1), signal(7), skill(1)

STANDARDS

       This command meets appropriate standards. The -L flag is Linux-specific.

AUTHOR

       Albert Cahalan <albert@users.sf.net> wrote kill in 1999 to replace a bsdutils one that was not standards  compliant.   The  util-linux  one
       might also work correctly.

REPORTING BUGS

       Please send bug reports to <procps@freelists.org>

procps-ng                                                          October 2011                                                            KILL(1)
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