Output text between two PATTERNS if text matches a CRITERIA [duplicate] - linux

Question

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grep lines matching a pattern, and the lines before and after the matching until different pattern
(4 answers)
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I want to select blocks between PATTERN1 and PATTERN2 if text inside the block contains CRITERIA, otherwise discard the whole block.
Sample task:
Select text between PATTERN1='start' and PATTERN2='end', if some text between 'start' and 'end' matches CRITERIA='DCE', then output the whole block between 'start' and 'end'.
Sample input:
start
123
ABC
123
end
start
123
DCE
123
end
start
123
EFG
123
end
Sample output:
start
123
DCE
123
end
I've tried the following using awk, but couldn't find how to use CRITERIA between two patterns:
awk '/start/,/end/' input_file

Answer 1

EDIT: As per OP a Input_file may have match at the end too and may not have end string, so adding code as per that too now.
awk '
/start/{
if(val) { print value };
flag=1;
value=val=""}
/[dD[cC][eE]/ && flag { val=1 }
/end/ { flag="" }
flag{
value=value?value ORS $0:$0
}
END{
if(val) { print value }}
' Input_file
Explanation:
awk '
/start/{ ##Looking for string start in a line if found then do following.
if(val) { print value }; ##Checking if variable val is NOT NULL, if yes then print variable of value.
flag=1; ##Setting variable named flag as 1 here.
value=val=""} ##Nullifying variables value and val here.
/[dD[cC][eE]/ && flag { val=1 } ##Searching string DCE/dce in a line and checking if variable flag is NOT NULL then set variable val as 1.
/end/ { flag="" } ##Searching string end in current line, if found then Nullifying flag here.
flag{ ##Checking if variable named flag is SET or NOT NULL here.
value=value?value ORS $0:$0 ##Creating value whose value is current line value and concatenating in its own value.
}
END{ ##Starting END block of awk here.
if(val) { print value }} ##Checking if variable val is NOT NULL then print variable value here.
' Input_file
Could you please try following awk and let me know if this helps you.
awk '/start/{if(val){print value};flag=1;value=val=""} /[dD[cC][eE]/ && flag{val=1} /end/{flag=""} {value=value?value ORS $0:$0}' Input_file
Adding a non-one liner form of solution too here.
awk '
/start/{
if(val) { print value };
flag=1;
value=val=""}
/[dD[cC][eE]/ && flag{ val=1 }
/end/ { flag="" }
{
value=value?value ORS $0:$0
}
' Input_file

Answer 2

Since the start-end blocks are separated by empty rexords, you can use those for separating instead. Here with awk:
$ awk 'BEGIN{RS=""}/DCE/' file
start
123
DCE
123
end
Edit: Since the empty records were not there after all, let's separate with ends:
$ awk 'BEGIN{RS=ORS="end\n"}/DCE/' file
start
123
DCE
123
end