how to print a variable inside while, outside of the loop.

basusimply · 09-18-2013, 01:19 PM

My input file and script look like:-

vi input
chg//okm/entk

vi find.sh
#########
forward=/
count=0
cat /root/script/input | while read -n1 char
do
if [ "$char" == "$forward" ];then
count=$(($count + 1))
fi
done
echo "$count"
#########

but the problem is, when I try running the script it prints 0. But It should print 3.Kindly help me please...

danielbmartin · 09-18-2013, 01:48 PM

Help us to help you. Provide a sample input file (10-15 lines will do). Construct a sample output file which corresponds to your sample input and post both samples here. With "Before and After" examples we can better understand your needs and also judge if our proposed solution fills those needs.

Daniel B. Martin

basusimply · 09-18-2013, 02:36 PM

thanks daniel...

My intention of writing this script was to count the no. of forward slashes in a particular line or a file(whatever it may be) which contains some forward slashes.
I'm not getting any specific output from this script.
There may be some way to print a variable(which is inside a while loop) outside the while loop.Here in this script its printing the previously declared $count value, not the count value(which got updated inside while loop).So I am seeking help.

Firerat · 09-18-2013, 02:51 PM

the pipe cuases while to be a subshell, so that subshell's local vars. are lost

replace

Code:

cat /root/script/input | while read -n1 char
do
if [ "$char" == "$forward" ];then
count=$(($count + 1))
fi
done

with

Code:

while read -n1 char;do
if [ "$char" == "$forward" ]; then
 count=$(($count + 1))
fi
done <<< /root/script/input

that should behave as you expect it to

Edit: see post 6 below, added the red to code above

astrogeek · 09-18-2013, 02:51 PM

Quote:

Originally Posted by basusimply

There may be some way to print a variable(which is inside a while loop) outside the while loop.Here in this script its printing the previously declared $count value, not the count value(which got updated inside while loop).So I am seeking help.

Firerat has it...

Firerat · 09-18-2013, 03:04 PM

hmm,

is /root/script/input a file?
I think you wanted echo and not cat..
and you seldom need cat ( do a websearch for "useless cat" or "useless use of cat"
anyway, even with echo it won't work, due to the pipe involking a subshell

try this

Code:

done <<< /root/script/input

<<< is passing what follows to stdin, it could be the output of a subshell
example

Code:

done <<< $(echo /root/script/input)

but as you will see, no need for that subshell in this case

basusimply · 09-18-2013, 03:10 PM

thanks a lot Firerat....its working as I wanted.....again many many thanks..

Firerat · 09-18-2013, 03:22 PM

the "Herestring:" ( <<< )
is touched upon here
http://mywiki.wooledge.org/BashGuide/InputAndOutput
some good stuff http://mywiki.wooledge.org/BashGuide/

other reading
http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-3.html
http://www.tldp.org/LDP/abs/html/

many more, but my bookmarks are a mess