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sed and line reading

 
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# 1  
Old 10-17-2005
sed and line reading
Hello all,

I'm stuck and can't seem to get my head into it. But what I'm trying to do is read a file and only read the 1st and evey 3rd line until the end of the file. I thought that sed -n '1,${p;n;n;n;}' would do it but I don't get the result of ervery 3rd line I get the whole file. There are is 1 hidden char in the file but I can't seem to make the sed command read these char and print the ervery 3rd line. Any help or led would be great.
The hidden char is a $. I found this when I use sed -n -e 'l' file_name.

THANKS ALL
# 2  
Old 10-17-2005
You lost me with hidden dollar sign stuff. Ignoring that, try this...
sed -n 'p;n;n;D'
# 3  
Old 10-17-2005
Thanks for the answer. Can you explain the D in the expression?

Thanks
# 4  
Old 10-17-2005
After the last n we have a line in the pattern space. D gets rid of it.
 
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