Get all lines in a big file containing some text:

cat filename  | egrep "141.71.45.20|159.205.92.236|171.33.185.210|"

Thanks to Günter!

dig domainname.tld

To really see all DNS entries for the domain, add option ANY:

dig domainname.tld ANY

Fast and easy if the linenumber is known:

find . -type f -not -iname "*.jpg" -not -iname "*.jpeg" -not -iname "*.gif" -not -iname "*.png" -not -iname "*.pdf"

Useful!

Split the file into multiple files at every 3rd line . i.e, First 3 lines into F1, next 3 lines into F2 and so on:

$ awk 'NR%3==1{x="F"++i;}{print > x}' filename

Change permission of directories

cd /var/files/test
find -type d -exec chmod 0777 {} \;

Useful to copy directories from one server to another:

cd into the dir you want to have your data

scp -prq username@127.0.0.1:/var/www/comefromdir/ .

For example: Change Collation in a big database dump.

cat dumpname | sed s/CHARSET=utf8/CHARSET=utf8\ COLLATE=utf8_unicode_ci/ > neuer_dumpname

• Install imagemagick
• Create newdir and copy images to be resized into it
• cd into newdir

mogrify -format jpg -resize "800x500>" *

$ sed '/WORD1/,/WORD2/d' input.txt > output.txt