I am using the following code to read line by line from a file, however my problem is that $value=0 at the end of the loop possibly because bash has created a subshell for the loop or something similar. How can I solve this.


value=0;

while read line
do
value=`expr $value + 1`;
echo $value;
done < "myfile"

echo $value;


Note: This example just counts the number of lines, I actually desire to do more complex processing than this though, so 'wc' is not an alternative.


Thanks Darren.

Hi Daren,
use awk for complex processing.
for example :


value=`cat myfile | awk ' BEGIN { FS=":"}
{
# here jou can use all complex processing from awk
# for loops / while loops / if then else / etc.
x=x+1
} END {
print x
}'`
echo $value #give the same output as your script

# what do you want to do
# tell it by example

In your example $value should be the number of lines in "myfile". Check that the file is not empty, or that you've typoed somewhere. Which version of bash? Which platform?

Backquotes do start a subshell, with the performance overhead that implies. You could use the shell's integer arithmetic funtions with the "let" command e.g.
let value=$value+1