头和grep同时

Question

是否有一个unix one liner来做这件事？

head -n 3 test.txt > out_dir/test.head.txt
grep hello test.txt > out_dir/test.tmp.txt
cat out_dir/test.head.txt out_dir/test.tmp.txt > out_dir/test.hello.txt
rm out_dir/test.head.txt out_dir/test.tmp.txt

即,我想同时从给定文件中获取标题和一些grep行.

Answer 1

你可以说:

{ head -n 3 test.txt ; grep hello test.txt ; } > out_dir/test.hello.txt

Answer 2

使用awk:

awk 'NR<=3 || /hello/' test.txt > out_dir/test.hello.txt