27.17 Finding a Character in a Column

Here's an idea for finding lines that have a given character in a column. Use the following simple awk (33.11 ) command:

% awk 'substr($0,

n

,1) == "

c

"'

 filename

where c is the character you're searching for, and n is the column you care about.

Where would you do this? If you're processing a file with very strict formatting, this might be useful; for example, you might have a telephone list with a # in column 2 for "audio" telephone numbers, $ for dial-up modems, and % for fax machines. A script for looking up phone numbers might use an awk command like this to prevent you from mistakenly talking to a fax machine.

If your data has any TAB characters, the columns might not be where you expect. In that case, use expand (41.4 ) on the file, then pipe it to awk .