如何只将字符串“ip”grep 到文件中？

Question

I am trying to find every way to find a string in some text. I want to find more ways using grep or sed. (bear in mind It's case sensitive)

• Every word (strings) containing string "ip" and redirect the output result in /root/found;

grep ip /usr/share/dict/words/ > /root/found

• Just words (strings) initiating with "ip" and redirect the output result in /root/found;

grep ^ip  /usr/share/dict/words > /root/found

• Just the word "ip" and redirect the output result in /root/found;

grep ^ip$ /usr/share/dict/words > /root/found

Answer 1

If you prefer to append output into file /root/found instead using > you have to use >>

Grep over irrespective of case:

grep -i "ip" /ust/share/dict/words >> /root/found 

If you want to search all files in sub directories and current directories of /ust/share/dict/words

find /ust/share/dict/words -name "*" -exec grep "ip"  '{}' \; -print  >> /root/found