How to egrep the first character in second column?

Question

Using egrep, how can I print all lines where last names start with K or k?

Jennifer Cowan:548-834-2348:583 Laurel Ave., Kingsville, TX 83745:10/1/35:58900
Lesley Kirstin:408-456-1234:4 Harvard Square, Boston, MA 02133:4/22/62:52600
Jennifer Cowan:548-834-2348:583 Laurel Ave., kingsville, TX 83745:10/1/35:58900
Lesley kirstin:408-456-1234:4 Harvard Square, Boston, MA 02133:4/22/62:52600
William Kopf:846-836-2837:6937 Ware Road, Milton, PA 93756:9/21/46:43500
Arthur Putie:923-835-8745:23 Wimp Lane, Kensington, DL 38758:8/31/69:126000

Answer 1

A first attempt would be

  grep '^[^ ]*  *[Kk]'

But this assumes that there is always exactly one firstname and no initials.
In this example you can use the -i option and replace [Kk] with just k

It might be better to latch on to the first colon

  grep -i ' k[^:]*:'

If you really want to print just the lastname, and not the whole line, you should consider using awk (or perl)

---

Update: heres how the first grep expression '^[^ ]* *[Kk]' is constructed

  '     apostrophe delimits a parameter that contains spaces
        and other so-called meta-characters that the shell might alter
  ^     caret means start of line
  [     brackets mark a set of characters, any one of which is to be matched
  ^     inside brackets means negation or 'none of the following'
        so `[^ ]` means "not a space"
  ]     is the end of the set.
  *     means 0,1 or more of the prior character
        so `[^ ]*` means any contiguous group of characters that does not 
        contain a space
  then we have two spaces
  *     means 0,1 or more of the prior character
        so space space * means 1 nor more spaces.
  [Kk]  means `K` or `k`
  [^:]* means 0,1 or more characters that are not a colon
  :     followed by a colon

Answer 2

perl -aF/:/ -ne 'print if $F[0] =~ /\s[Kk]\S+$/'

• With -aF/:/, the entire line is split into colon-separated fields;
• $F[0] is the zeroth field and contains the names;
• /\s[Kk]\S+$/ matches a space (\s), followed by K or k, followed by any number of non-space characters (\S+) until the end of the field ($).