Grep
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Let's prepare a file with various character lenghts, so that we can use our grep
commands later on:
$ i=1; for c in {a..z}; do perl -e "print \"${c}\"x${i}; print \"\n\""; i=$((i+1)); done a bb ccc dddd eeeee ffffff ggggggg hhhhhhhh iiiiiiiii jjjjjjjjjj kkkkkkkkkkk llllllllllll mmmmmmmmmmmmm nnnnnnnnnnnnnn ooooooooooooooo pppppppppppppppp qqqqqqqqqqqqqqqqq rrrrrrrrrrrrrrrrrr sssssssssssssssssss tttttttttttttttttttt uuuuuuuuuuuuuuuuuuuuu vvvvvvvvvvvvvvvvvvvvvv wwwwwwwwwwwwwwwwwwwwwww xxxxxxxxxxxxxxxxxxxxxxxx yyyyyyyyyyyyyyyyyyyyyyyyy zzzzzzzzzzzzzzzzzzzzzzzzzz
Find strings at least 3 characters long:[1]
grep -E '^[[:alpha:]]{3}$' file.txt
Find (and print only) words in a file:[2]
grep -Eo '\w+' file.txt
Print last 3 characters[3] of a string:
grep -o '.\{3\}$'