Shell Programming and Scripting

I have written a script that I want to be repeated. The script that I wrote outputs the date, how many people are on the system, how many people logged in before me, and how many people logged in after me. Than what I want it to do is after it outputs the 4 lines I want it to go back to the beginning and start over. How would I go about doing this without using a loop. Is there a command in unix that does this? Thanks for your help.

Not sure , why are you trying to do this with out loop.

You have to run the script having 4 lines manually whenever you want to ,
with out the help of loops.

if you really want to loop without a loop ...

make sure the commands you want to run are in a function in the script ... then at the end of the function ... add a line to call the function again ...

call the function ...

be forewarned that like regular loops, not putting in an escape clause or the proper conditional parameters in the function will put you into an indefinite loop which most likely is not what you want ...

Code:

#! /bin/ksh
# yourscript.ksh

not_a_loop_function(){
    date
    who | wc -l
    ...
    ...
    not_a_loop_function
}

not_a_loop_function
exit 0

or ... if you want to just use your script ... add a line towards the end of your script that calls your script again ... same caveats as above ... also might not be want you want as it might create too many subshells depending on how your script is written ... better off using the function method above ...

Code:

#! /bin/ksh
# yourscript.ksh

command
command
...
...

yourscript.ksh
exit 0

you might "really" want to put in some code to pause the non-loop --- i.e., sleep 5 --- as well as to break it based on some input to control it better ... (the code below will keep rechecking until you give it "n" or "q" when asked the recheck question at which point it will exit)

Code:

#! /bin/ksh
# yourscript.ksh

not_a_loop_function(){
    date
    who | wc -l
    ...
    ...
    echo "check again? (y,n,q) \c"
    read ans
    case $ans in
    n|q) echo "bye!"
         exit 0 ;;
    *)   not_a_loop_function ;;
    esac
}

not_a_loop_function
exit 0

You can do infinite loop of same commands as,

#way1 - with infinite while loop
#!/bin/sh
while true; do

date
who | wc -l
..
# Sleep for some time to make loop again
sleep 2
done
exit 0

# way2 - with cron
#!/bin/sh
date
who | wc -l
..

exit 0

# chmod 755 <script>
crontab -e
* * * * * <script with absolute path> 1>/dev/null 2>&1

so that script will be executed everyday on everyday hour..

HTH.

actually you might want to do this ... or else it will be run every minute on every hour ...

Code:

0 * * * * <script with absolute path> 1>/dev/null 2>&1

btw, running the script through cron will send the output somewhere else other than the console so you might want to send the output to a file somewhere so you can read it ... otherwise you'll get emails from root regarding the output of your cron job ...