-h # do not show filename
-i # no case
-r # recursive
-o # show only mattching word of the line
-v # invert match
-l # display only the file names which matches the given pattern
grep -r foo . # grep for 'foo' in current folder
grep -e '-X' # use -e when pattern has a leading '-'
grep -v '^$' file # remove blank lines
ps ax | grep ssh | grep -v grep # list ssh processes without grep process
tail -f | grep -E 'error|' # colorize 'error' in tail
grep --color='auto' -P -n "[\x80-\xFF]" file # grep for non-ASCII Characters
cat file1 | grep -f - file2 # grep for pattern from file1 in file2
grep -o '.' file.txt | sort | uniq -c # letter distribution of all words in file.txt