Scrutinizer's code makes assumptions about what the 1st line of a header looks like (based on your sample input) that might not be true in your real data and only requires that the 3rd line of a header contain From= somewhere on the line. It will also delete a 3 line header if the next 3 line header is the same as the previous 3 line header even if those headers are not adjacent.
The following code makes no assumptions about what the 1st two lines of a 3 line header look like, assumes that the 3rd line must start with From= and must also contain , To=. It will only remove a 3 line header if the next three lines match that header. I asked questions about the header format (all three lines) and got no response, so I still have no idea if the following code will do what is desired. I believe it meets all stated requirements:
FWIW I tried it with the emulator link you provided:
Code:
/var/root # cat test.sh
awk -F, '
NF==4 && $1~/^[0-9]+$/ { # If there are 4 fields and
the first field is numerical, then found a header
is_header=1
}
is_header {
current=current $0 ORS # Add lines to current header
if(/From=/){ # Last line of header
if(current!=previous) printf "%s", current
previous=current
current=""
is_header=0
}
next
}
1
' File.txt
Scrutinizer's code makes assumptions about what the 1st line of a header looks like (based on your sample input) that might not be true in your real data and only requires that the 3rd line of a header contain From= somewhere on the line. It will also delete a 3 line header if the next 3 line header is the same as the previous 3 line header even if those headers are not adjacent.
[..]
Good catch about the adjacency, Don. Quick fix:
Code:
awk -F, '
NF==4 && $1~/^[0-9]+$/ { # If there are 4 fields and the first field is numerical, then found a header
is_header=1
previous=current
current=""
}
is_header {
current=current $0 ORS # Add lines to current header
if(/From=/){ # Last line of header
if(current!=previous) printf "%s", current
is_header=0
}
next
}
{
current=""
}
1
' file
But further robustness would need to be added and "From=" would need to be always present...
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NAMES
John
carrey
williams
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05-31-2014
