grep previous line of the matched string

namishtiwari has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks, Here is my piece of code, Inside a loop i am calling this--

if($line =~ /Auth\s+failed.*/)
        {
            $ErrorMsg=$1;
            printf "Failure,";
            while ( $line = <$log> )
            {
                if ($line =~ /ArAuthFrameworkImpl::doPostAuth.*Authent
+ication\s*mechanism\s*returned\s*\[(\d+)\]/)
                {
                    printf FP_OUT "${1}, $ErrorMsg\n";
                    return;
                }
            }
            
        }
[download]

here is the log snippet--

Arcot Native Server: recvd AA_BIN_MSG_VER_CHG
Wed May 20 05:22:58.368 2009 Morocco Standard Time INFO:    pid 2172 t
+id 3412: 170: 10106934: Cert Subject String....:[ UserID=123456; Card
+Name=CARD]
Wed May 20 05:22:58.368 2009 Morocco Standard Time INFO:    pid 2172 t
+id 3412: 170: 10106934: Cert issuer............:
Wed May 20 05:22:58.368 2009 Morocco Standard Time INFO:    pid 2172 t
+id 3412: 170: 10106934: Cert serial String.....:[75fa]
Wed May 20 05:22:58.368 2009 Morocco Standard Time INFO:    pid 2172 t
+id 3412: 170: 10106934: ArcotException verifying Arcot challenge: [Ar
+cot Exception,Certificate expired or not yet valid: certificate expir
+ed or not yet valid in ArcotVerifier], Challenge verification failed 
+for 
Wed May 20 05:22:58.368 2009 Morocco Standard Time INFO:    pid 2172 t
+id 3412: 170: 10106934: ApricotID Credential Expired. serial : [75fa]
Wed May 20 05:22:58.368 2009 Morocco Standard Time INFO:    pid 2172 t
+id 3412: 170: 10106934: Auth failed due to Account Verification(seria
+l Number [75fa])
[download]

in $Error_Msg i want to capture the line "ApricotID Credential Expired". I just want to know how to capture the previous line of the matching string. Thanks NT

Comment on grep previous line of the matched string Select or Download Code

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Re: grep previous line of the matched string by Transient (Hermit) on Jul 02, 2009 at 16:36 UTC
`my $prev_line = ""; while ( my $line = <$log> ) { if ( $line =~ /Auth\s+failed./ ) { ... # error message should be in $prev_line } $prev_line = $line; }` [download]	[reply] [d/l]