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Grep first n lines from each file


 
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# 1  
Old 04-28-2020
Grep first n lines from each file

I am using



Code:
grep --include="*.org" --include="*.texi" -hir -C 8 "Abstract" ./


Now I would simply like to print the first n lines from each file without searching for any pattern.
# 2  
Old 04-28-2020
man head
# 3  
Old 04-28-2020
Sure head could work. However I would have to specify a file name. It will not behave same way as when using grep for searching all files.
# 4  
Old 04-28-2020
ok, how about using find. To start with:
Code:
find . \( -name '*.org' -o -name '*.texi' \) | xargs head


Last edited by vgersh99; 04-28-2020 at 01:00 PM..
This User Gave Thanks to vgersh99 For This Post:
# 5  
Old 04-28-2020
grep -l prints the file names so you can process them with xargs.
Code:
grep --include="*.org" --include="*.texi" -lir "Abstract" . | xargs head

But xargs has a problem with space characters in file names.
find -exec handles spaces well:
Code:
find . \( -name '*.org' -o -name '*.texi' \) -exec grep -iq "Abstract" {} \; -exec head {} +

grep -q suppresses output; the exit status decides on the following.
Probably all find versions cannot chain {} + queues so there is a need for a slower {} \;.
Many GNU utilities allow 0-byte terminated lines, so the following is fast and correct:
Code:
grep --include="*.org" --include="*.texi" -lirZ "Abstract" . | xargs -0 head

This User Gave Thanks to MadeInGermany For This Post:
# 6  
Old 04-28-2020
Unfortunately, awk doesn't have the --recursive option that grep provides. But we can resort to bash's "brace expansion" for sweeping across the directory tree and "extended globbing" ("extended pattern matching"). Try
Code:
$ awk -v"LINE=$n" 'FNR <= LINE'  {*,*/*,*/*/*}.@(org|texi)

and adapt the */*/* globs to taste. If you want the filename printed, extend to
Code:
$ awk -vLINE=$n 'FNR==1 {print FILENAME} FNR <= LINE'  {*,*/*,*/*/*}.@(org|texi)

, and you even check the n lines for your pattern:
Code:
$ awk -vLINE=$n 'FNR==1 {print FILENAME} /Abstract/ && FNR <= LINE'  {*,*/*,*/*/*}.@(org|texi)

This User Gave Thanks to RudiC For This Post:
# 7  
Old 04-29-2020
Even without the shopt -s extglob the folllowing is expanded: echo {*,*/*,*/*/*}.{opt,texi}
A shopt -s nullglob suppresses non-matching patterns.

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