regular expressions

[Ashwin Khandare]

hi everybody   Can anyone tell me how do I search and replace a pattern in file using shell(BASH).   file abc.txt contains Sep 15 14:18:54 203.146.91.228:23 202.88.143.72:23     The time 14:18:54 (hours:mins:secs) needs to be replaced by 14:18 (hours:mins) for "n" number of lines in a file   Thanks in advance   Thanks & Warm Regards ======================= Ashwin Khandare Engineer Western Outdoor Interactive   --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.381 / Virus Database: 214 - Release Date: 8/2/02