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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.
while read line
value=`expr $value + 1`;
done < "myfile"
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, nor is perl im afraid.
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Bash's sh emulation (that is if a script is called with /bin/sh instead of /bin/bash) does not spawn a subshell for that kind of while loop invloving IO redirection. Traditional sh as the one found in Solaris does.
A quick and dirty solution would be to save the result in a temporary file.
Hi, I don't know if anyone still reads this but when I try to read a file line by line, I use something like "head -n $x filename | tail -n 1" where $x loops from 1 through the amount of lines in the file which can easily be found using "wc -l filename"
Does this make any sense or isn't it what you're looking for.
In fact, what's bothering me is that wc doesn't just return the number of lines in the file but also the name of the file which made it unusable in a conditional statement... (damn you! damn you, wc!)
I had to trick it like this:
# read a file line by line
lns=`wc -l $file`
y=`expr "$lns" : '\([0-9]*\)'`
while [ "$x" -lt "$y" ]
head -n $x $file | tail -n 1
If you see a more elegant way, please let me know.