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odd problem in read lines from file

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# 1  
Old 09-01-2011
odd problem in read lines from file
Hi,

I wrote a small program to read lines from a file and count the lines. The program is as below:

Code:
filename=$1
count=0    
cat $filename | while read -r line
do  
    printf "%5d:%s\n" $count "$line"
    count=$((count + 1))
done
echo " $count "

After I run the program, the result is below:
Code:
   0:This
    1:is
    2:test
    3:
    4:!
    5:
 0

I don't understand why the count is still 0 after the read lines loop. Can someone give any advices? Thanks!
Last edited by Franklin52; 09-01-2011 at 01:24 PM.. Reason: Please use code tags for data and code samples, thank you
# 2  
Old 09-01-2011
BashPitfalls - Greg's Wiki
# 3  
Old 09-01-2011
Hi yazu,

Thanks. The information is very helpful.
# 4  
Old 09-01-2011
This is a useless use of cat. In this case the useless cat doesn't just waste CPU time, it also prevents variables from being modified because the things after the pipe execute in a subshell. Remove the useless cat and it should work:
Code:
filename=$1
count=0    
while read -r line
do  
    printf "%5d:%s\n" $count "$line"
    count=$((count + 1))
done < $filename
echo " $count "

# 5  
Old 09-01-2011
Hi Corona688:

Thanks!
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