UNIX for Dummies Questions & Answers

Hi all,
I am looking to find all words from a certain file that satisfy the following constraint: The words are 3 letters long. The first letter is either a 'b' or a 'c' while the other letters are the same. For example, if my file contains
bat
cat
boo
coo
bob
cam

the output should be (bat,cat, boo,coo). Any idea on how to do this with grep? Thanks in advance for the help.

Is this for a classroom assignment?

What have you tried so far?

Not a classroom assignment. I am trying to create a puzzle which needs such a constraint. I have very little knowledge of unix/grep and my only prior experience is using grep to search for words from a dictionary in some other word puzzles.

This processes to get the 2nd and 3rd letter of common words. You should be able to add the b/c to the beginning of the output.

Code:

> cat file94
bat
cat
boo
coo
bob
cam

> cat manip94
#! /usr/bin/bash

grep "^b" file94 | cut -c2-3 | sort >file94b
grep "^c" file94 | cut -c2-3 | sort >file94c

comm -12 file94b file94c >file94_1

cat file94_1

Script execution

Code:

> manip94
at
oo

'the other letters are the same' - is that the same in the same WORD or across words?
If the former, the output should be 'boo' and 'coo'.
If the latter, not sure if it can be done with 'grep' only.

This will only show the lines that are 3 letters and starts with b or c, all lowercase.
Maybe this will give you ideas. but asvgersh99 says I dont think you can do it all with just grep.

Code:

grep '^[bc][a-z]\{2\}$' test.txt

Thanks for all your responses. I am trying out what joeyg has suggested. It seems to work adequately for my purposes. Again, thanks for the help.