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Top Forums UNIX for Advanced & Expert Users Bourne shell script need help please ? Post 9123 by LivinFree on Tuesday 23rd of October 2001 05:42:36 AM
Old 10-23-2001
Well, first off, it helped me a lot to look at the code with indents in it:
Code:
#!/bin/ksh
count=1 
val=$2 
op=$1 
ans=0 
if [ $op = "-e" -o $op = "-o" ] 
then 
     if [ $op = "-e" ] 
     then 
     while [ $count -le $val ] 
     do 
     ans=`expr $count % 2` 
          if [ $ans -eq 0 ] 
          then 
          echo "$count \c " 
          count=`expr $count + 1` 
          fi 
     done 
     elif [ $op = "-o" ] 
     then 
     while [ $count -le $val ] 
     do 
     ans=`expr $count % 2` 
          if [ $ans -ne 0 ] 
          then 
          echo "$count \c " 
          count=`expr $count + 1` 
          fi 
     done 
     fi 
else 
while [ $count -le $val ] 
do 
echo "$count \c " 
count=`expr $count + 1` 
done 
fi

Now, the first thing I usually try when trying to figureout what my script is doing is to add a "set -x" line at the top of the script. That will echo out each step the shell is performing, so you can see what's going on...

So, The way I ran the script, (I'll give an example of what I think I saw trying to use the" -e 4 "option) it got stuck in a loop at:
+ ans=1
+ '[' 1 -eq 0 ']'
+ '[' 1 -le 4 ']'
++ expr 1 % 2
Ok, interesting... let's look at this. So, what the script is doing step by step:
Code:
     if [ $op = "-e" ]                       # This is true in our case
     then 
     while [ $count -le $val ]          # while 1 is less than or equal to 4
     do 
     ans=`expr $count % 2`         # ans = 1 % 2, or ans = 1
          if [ $ans -eq 0 ]                  # if ans (1) = 0, then continue... nope - can't continue
          then 
          echo "$count \c " 
          count=`expr $count + 1` 
          fi                                         # We're done, time to loop while waiting for ans to equal 0

Do you see what you problem is? Hint: $ans will always equal 1 in this case

Here's another (messier, but more info) way of doing it:
Code:
if [ "$op" = "-e" -o "$op" = "-o" ]
echo " if [ $op = -e -o $op = -o ]"
        then
echo "     then"
        if [ "$op" = "-e" ]
echo "     if [ $op = -e ] "
        then
echo "     then"
        while [ "$count" -le "$val" ]
echo "     while [ $count -le $val ] "
        do
echo "     do"
        ans=`expr $count % 2`
echo "     ans=`expr $count % 2` "
                if [ "$ans" -eq "0" ]
echo "          if [ $ans -eq 0 ] "
                then
echo "          then"
                echo -e "$count \c "
echo "          echo -e $count \c"
                count=`expr $count + 1`
echo "          count=`expr $count + 1`"

This way, you can watch your script in action... It almost looks as if it doesn't know when to exit, right?

You may need a little re-designing, but I think you're pretty much on the right track

(Ooh, and I appologize, I changed some of the "echo"'s to "echo -e"'s, since I was looking at this on a Linux system...

Does this help any?
 

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TPING(1)							   LAM COMMANDS 							  TPING(1)

NAME
tping - Send echo messages to LAM nodes. SYNOPSIS
tping [-hv] [-c count] [-d delay] [-l length] nodes OPTIONS
-h Print the command help menu. -v Turn OFF verbose mode. -c count Send count messages. -d delay Delay delay seconds between each message. -l length Each message is length bytes long. DESCRIPTION
The tping command sends messages to, and collects replies from, a list of nodes, via the LAM echo server. It is similar to the UNIX ping(8) command, and is used as a quick diagnosis of the LAM network. Unless options are specified, tping sends a 1 byte message an infinite number of times, displaying the roundtrip time of each message as it completes, with a delay of 1 second between roundtrips. After the loop is broken (with keyboard interrupt, eg: ^C), tping prints statis- tics about all roundtrip messages. EXAMPLES
tping h Echo messages to the local node. tping -v n7 -l 1000 -c 10 Echo 1000 byte messages to node 7. Stay silent while working. Stop after 10 roundtrips and report statistics. BUGS
There is no built-in timeout and tping will wait forever to receive an echo. If no echo is received, due to a dead link or node, tping hangs. Stop the process with a keyboard suspend signal (eg: ^Z) and terminate LAM with lamhalt(1) or lamwipe(1) (although the use of lamwipe(1) is deprecated). SEE ALSO
lamhalt(1), lamwipe(1) LAM 7.1.4 July, 2007 TPING(1)
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