How to copy a range of lines from a start and end pattern (excluding start & end pattern) and paste into a third pattern of the same file

Question

Original file

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startpattern
   text to copy 1
   test to copy 2
endpattern
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thirdpattern

Result file

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startpattern
   text to copy 1
   test to copy 2
endpattern
.
.
.
thirdpattern
   text to copy 1
   test to copy 2
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.

Answer 1

This seems pretty straight-forward with the scriptable editor ed. The core command is:

/startpattern/+1, /endpattern/-1 t /thirdpattern/

You could change the file with the command-line:

printf '%s\n' '/startpattern/+1, /endpattern/-1 t /thirdpattern/' w q | ed -s filename

... which pipes three commands into ed's input buffer: the main command, the write command, and the quit command.

You would/should tighten the regular expressions on each of the patterns to be sure that you're capturing the correct lines. The +1 and -1 on the first two patterns adjust the match forwards and backwards to exclude the lines with those two patterns.