#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?i)^\S*\S+\s+[a-fA-F0-9.]+\s+DATA\s+Auth\s+(\S+)\s*$"
Local $sString = "Gi1/0/25 0001.2e68.c47b mab DATA Auth 000000000000469AB6F2D0A2" & @CRLF & _
"Gi1/0/39 0c8d.dbc5.7da8 mab DATA Auth 000000000000466BB2BF922F" & @CRLF & _
"Gi1/0/8 7c4a.8201.a189 mab DATA Auth 00000000000046CFBA8ACF3E" & @CRLF & _
"Gi1/0/9 7c4a.8201.a506 mab DATA Auth 00000000000046CEBA8A9660" & @CRLF & _
"Gi1/0/15 0001.2e68.cc47 mab DATA Auth 00000000000046ACB6F35DE1" & @CRLF & _
"Gi1/0/18 0001.2e68.c66c mab DATA Auth 00000000000046AFB6F37505" & @CRLF & _
"Gi1/0/14 0001.2e68.c376 mab DATA Auth 00000000000046A9B6F3261B" & @CRLF & _
"Gi1/0/6 0012.e506.0307 mab DATA Auth 00000000000045CCAA38FB62" & @CRLF & _
"Gi1/0/2 0001.2e69.b955 mab DATA Auth 00000000000046B3B7ED23A6" & @CRLF & _
"Gi1/0/31 0001.2e68.c37f mab DATA Auth 00000000000046A5B6F303BA" & @CRLF & _
"Gi1/0/26 0001.2e68.c6a5 mab DATA Auth 000000000000469FB6F2E6BA" & @CRLF & _
"Gi1/0/1 0001.2e69.b98c mab DATA Auth 0000000000004675B2FF684C" & @CRLF & _
"Gi1/0/4 0001.2e69.b9ef mab DATA Auth 00000000000046B1B7ECAB2B" & @CRLF & _
"Gi1/0/5 0025.3601.7334 mab DATA Auth 00000000000046C5B9DD1F0F" & @CRLF & _
"Gi1/0/20 0001.2e68.c36f mab DATA Auth 00000000000046ABB6F3473A" & @CRLF & _
"Gi1/0/29 0001.2e68.c492 mab DATA Auth 000000000000469EB6F2D9E4" & @CRLF & _
"Gi1/0/36 0c8d.dbc5.5327 mab DATA Auth 0000000000004668B2BF89E6" & @CRLF & _
"Gi1/0/30 0001.2e5f.4561 mab DATA Auth 00000000000046C7BA45DDEB" & @CRLF & _
"Gi1/0/22 0001.2e68.c654 mab DATA Auth 00000000000046ADB6F35DE4" & @CRLF & _
"Gi1/0/27 0001.2e68.c6b4 mab DATA Auth 00000000000046A0B6F2EB5B" & @CRLF & _
"Gi1/0/13 0001.2e68.c35c mab DATA Auth 00000000000046A4B6F2FC37" & @CRLF & _
"Gi1/0/3 0025.36fe.c560 mab DATA Auth 00000000000043267E44A554" & @CRLF & _
"Gi1/0/37 0c8d.dbc4.f3a1 mab DATA Auth 0000000000004669B2BF8AFD" & @CRLF & _
"Gi1/0/21 0001.2e68.c4a6 mab DATA Auth 00000000000046AEB6F363FF" & @CRLF & _
"Gi1/0/19 0001.2e68.c6a0 mab DATA Auth 000000000000469CB6F2D68F" & @CRLF & _
"Gi1/0/16 0001.2e68.c66d mab DATA Auth 00000000000046A8B6F3213E" & @CRLF & _
"Gi1/0/42 0c8d.dbc5.5316 mab DATA Auth 000000000000466AB2BF9015" & @CRLF & _
"Gi1/0/17 0001.2e68.c6a8 mab DATA Auth 00000000000046AAB6F32DC0" & @CRLF & _
"Gi1/0/40 0c8d.dbc5.7a5b mab DATA Auth 000000000000466CB2BF99C0" & @CRLF & _
"Gi1/0/35 0c8d.dbc5.7003 mab DATA Auth 000000000000466DB2BF9B16" & @CRLF & _
"Gi1/0/23 0001.2e68.c489 mab DATA Auth 0000000000004697B6F2BABC" & @CRLF & _
"Gi1/0/10 7c4a.8201.a531 mab DATA Auth 00000000000046B6B8AF5E00" & @CRLF & _
"Gi1/0/41 0c8d.dbc5.7bb8 mab DATA Auth 000000000000466EB2BFB123" & @CRLF & _
"Gi1/0/38 0c8d.dbc5.775d mab DATA Auth 0000000000004667B2BF855D" & @CRLF & _
"Gi1/0/11 001b.eb45.7fd3 mab DATA Auth 00000000000046B9B936EB15" & @CRLF & _
"Gi1/0/28 0001.2e68.cd25 mab DATA Auth 000000000000468EB6A8476B" & @CRLF & _
""
Local $sSubst = "Gi1/0/25"
Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst)
MsgBox($MB_SYSTEMMODAL, "Result", $sResult)
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 AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm