Is there a problem with grep command? I am getting characters that don't match my regular expression

Question

I ran this command:

grep -i 'bro*' shows.csv

and got this as output

1845307,2 Broke Girls,2011,138,6.7,89093
1702042,An Idiot Abroad,2010,21,8.3,29759
903747,Breaking Bad,2008,62,9.5,1402577
2249364,Broadchurch,2013,24,8.4,89378
1733785,Bron/Broen,2011,38,8.6,56357
2467372,Brooklyn Nine-Nine,2013,145,8.4,209571
7569592,Chilling Adventures of Sabrina,2018,36,7.6,69041
7221388,Cobra Kai,2018,31,8.7,72993
1355642,Fullmetal Alchemist: Brotherhood,2009,69,9.1,111111
118360,Johnny Bravo,1997,67,7.2,32185
455275,Prison Break,2005,91,8.3,465246
115341,Sabrina the Teenage Witch,1996,163,6.6,33458
1312171,The Umbrella Academy,2019,20,8,140800
3339966,Unbreakable Kimmy Schmidt,2015,51,7.6,61891

Where is bro in breaking bad? In fact, o doesn't even appear in "Breaking bad". I tried it once more, and got the same result. It is not accounting for the last character. Is there something wrong in the way I am writing it?

You can download the file shows.csv from https://cdn.cs50.net/2021/x/seminars/linux/shows.csv

Answer 1

In your code o* means "zero or more occurrences of o". It seems you confused regular expressions with glob syntax (where o* means "one o and zero or more whatever characters").

In Breaking Bad there is exactly zero o characters after Br, so it matches bro* (case-insensitively).

grep -i bro shows.csv will do what (I think) you want.

Answer 2

Here the o* implies "zero or more". If you want the desired output with the asterisk, you can just add a random alphabet after o like this:

$ grep -i "broa*" shows.csv

1845307,2 Broke Girls,2011,138,6.7,89093 1702042,An Idiot Abroad,2010,21,8.3,29759 2249364,Broadchurch,2013,24,8.4,89378 1733785,Bron/Broen,2011,38,8.6,56357 2467372,Brooklyn Nine-Nine,2013,145,8.4,209571 1355642,Fullmetal Alchemist: Brotherhood,2009,69,9.1,111111

Else, grep -i "bro" shows.csv will work.

HTH.