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Old 02-27-2009, 01:07 AM   #1
ZAMO
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How to use a command inside sed


Hi all ,


Am trying to print the last n lines of a file using sed, but am unable to do a echo within sed. can someone correct me?


Code:
sed -n '1,40' linetest
is working

if n=40 (am got this from some other output)

I try to the following and failed.

Code:
sed -n '1,"/`echo $num`/"p' linetest
I want to print the first n lines only .I want a substitute for
Code:
head -`echo $num`  linetest
using sed.


Thanks
 
Old 02-27-2009, 01:42 AM   #2
sycamorex
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To print the last 5 lines of a file you would use:

Code:
sed -e :a -e '$q;N;6,$D;ba' file
To print the first 5 lines:

sed -n '1,5p' file

I don't know how to pass values to sed commands, though.
 
Old 02-27-2009, 04:19 AM   #3
ZAMO
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I got that with this option.

Code:
sed -n "1,`echo $num`p" linetest
Thanks sycamorex
 
Old 02-27-2009, 04:37 AM   #4
H_TeXMeX_H
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I usually do:

Code:
sed -n '1,'"$(echo $num)"'p' linetest
 
  


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