re = /^([A-Za-z]{3} {1,2}[0-9]{1,2} {1,2}([0-9]{2}:){2}[0-9]{2}).* (delay=([0-9]{2}):([0-9]{2}):([0-9]{2})).*/m
str = 'Mar 19 06:10:16 ip-172-2-0-53 sendmail[28131]: v2JDA1k4028131: to=root, ctladdr=root (0/0), delay=00:00:15, xdelay=00:00:00, mailer=relay, pri=30580, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (v2JDAG5W028134 Message accepted for delivery)
Mar 19 14:41:26 ip-172-2-0-53 sendmail[29483]: v2JLfNFN029481: to=<tsturdsi@ifaded.com>,<kgogineni@ifaded.com>, delay=00:00:03, xdelay=00:00:03, mailer=esmtp, pri=151738, relay=ifaded-com.mail.p...ction.outlook.com. [xx.xxx.x.x], dsn=2.0.0, stat=Sent (<4253fc91a05d91ce3b5f5147278dfae9@heg.jkadionbub.com> [InternalId=31288836753166, Hostname=ERGDGD5.namprd07.prod.outlook.com] 8924 bytes in 0.309, 28.142 KB/sec Queued mail for delivery)
Mar 19 06:10:26 ip-172-2-0-53 sendmail[28131]: v2JDA1k4028131: to=root, ctladdr=root (0/0), delay=00:20:15, xdelay=00:00:00, mailer=relay, pri=30580, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (v2JDAG5W028134 Message accepted for delivery)
'
subst = '\\4\\5\\6 \\1 \\3'
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html