Grep first n lines from each file

UNIX for Beginners Q & A
1

I am using

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

man head

3

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

ok, how about using find . To start with:

find . \( -name '*.org' -o -name '*.texi' \) | xargs head
3 Likes
5

grep -l prints the file names so you can process them with xargs.

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:

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:

grep --include="*.org" --include="*.texi" -lirZ "Abstract" . | xargs -0 head
3 Likes
6

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

$ awk -v"LINE=$n" 'FNR <= LINE'  {*,*/*,*/*/*}.@(org|texi)

and adapt the */*/* globs to taste. If you want the filename printed, extend to

$ awk -vLINE=$n 'FNR==1 {print FILENAME} FNR <= LINE'  {*,*/*,*/*/*}.@(org|texi)

, and you even check the n lines for your pattern:

$ awk -vLINE=$n 'FNR==1 {print FILENAME} /Abstract/ && FNR <= LINE'  {*,*/*,*/*/*}.@(org|texi)
3 Likes
7

Even without the shopt -s extglob the folllowing is expanded: echo {*,*/*,*/*/*}.{opt,texi}
A shopt -s nullglob suppresses non-matching patterns.

8

Hi
So, passed by ...

grep --include=*.{org,texi}

--- Post updated at 22:03 ---

Maybe I misunderstood something

grep -hrm8 '.' --include=*.{org,texi} ./
3 Likes