Array with do while and if loop

Shell Programming and Scripting
1

Hi All,
I am trying to run a do while for an array. And in the do while, I'm trying to get a user response. Depending on the the answer, I go ahead and do something or I move on to next element in the array.
So far I can read the array, but I can't get the if statement to work. Any suggestions will be greatly appreciated!

#!/bin/bash
set -x
linenum=1
array=
ps -ef | grep myAgent | grep -v grep | awk '{print $8}' | while read line ;
do
    echo "$linenum : $line"
    set -- $line
    echo "$1"
    array[$linenum]=$1
    echo "  Would you like to analyze this instance ${array[$linenum]} (y/n)? "
    read response  ### this does not work
                if [ "$response" = Y ] || [ "$response" = y ] ; then
                      echo "Analysing"
                      sleep 10
                      # do some thing.. code snip ..
                fi
    linenum=$(( linenum + 1 ))
done

Thanks for looking.
Nitin :slight_smile:

2 
ps -ef | awk '/myAgent/{print $8}' | while read line ;
....
if [ "$response" = Y ] -o [ "$response" = y ] ; then
1 Like
3

Because you're in the middle of a pipe chain, standard input is already being used. Your read just grabs the next line printed by awk!

You should tell it explicitly that you want to read from the terminal, like

read response < /dev/tty

/dev/tty is a special file that is always your current terminal.

---------- Post updated at 02:54 PM ---------- Previous update was at 02:51 PM ----------

Simplifying it like vgersh99 suggests is also a good idea. Reducing the number of things in your pipe chain will make your script much more efficient.

1 Like
4

here're a couple of alternatives:

#!/bin/ksh
set -x
linenum=1 
array= 
ps -ef | grep myAgent | grep -v grep | awk '{print $8}' |&
while read -p line
do
....

Or if you're reading from a file and want to prompt a user for input in the middle of a loop:

#!/bin/ksh

file=read.txt

exec 3< $file

while read -u3 f
do
  printf 'Your input? (y/n) '
  read answer
  if [ "${answer}" = y ] -o [ "${answer}" = Y ]; then
    echo "answer->[${answer}] readFile->[${f}]"
  fi
done
5

Thanks for the quick replies. I was able to get the read to work.
But for some reason I was not getting inside the if condition loop. I kept getting this error:

./test_agent.sh: line 15 [: too many arguments

Turns out the if statement cannot handle -o or ||. Strange, but that's a problem for some other day.
My code looks like this now, I thought about awk '/myAgent/{print8}', but I then get an extra line with just awk. So I'll have to do a grep -v awk.

#!/bin/bash
linenum=1
array=
ps -ef | grep myAgent | grep -v grep | awk '{print $8}' | while read -p line ;
# or this:
# ps -ef | grep -v awk | awk '/myAgent/{print $8}' | while read line ;
#
do
    echo "$linenum : $line"
    set -- $line
    echo "$1"
    array[$linenum]=$1
        echo "  Analyze instance echo ${array[$linenum]} (y/n)? "
                read answer  </dev/tty
                if [ "$answer" = Y ]  ; then
                echo "Analysing"
                # do something
                fi
    linenum=$(( linenum + 1 ))
done

Thanks.
Nitin :b:

6

Or, you could just use awk '/[m]yAgent/{print $8}'

1 Like