How to print lines between two patterns, inclusive or exclusive (in sed, AWK or Perl)?

Question

I have a file like the following and I would like to print the lines between two given patterns PAT1 and PAT2.

Answer 1

You can do what you want with sed by suppressing the normal printing of pattern space with -n. For instance to include the patterns in the result you can do:

$ sed -n '/PAT1/,/PAT2/p' filename
PAT1
3    - first block
4
PAT2
PAT1
7    - second block
PAT2
PAT1
10    - third block

To exclude the patterns and just print what is between them:

$ sed -n '/PAT1/,/PAT2/{/PAT1/{n};/PAT2/{d};p}' filename
3    - first block
4
7    - second block
10    - third block

Which breaks down as

• sed -n '/PAT1/,/PAT2/ - locate the range between PAT1 and PAT2 and suppress printing;

• /PAT1/{n}; - if it matches PAT1 move to n (next) line;

• /PAT2/{d}; - if it matches PAT2 delete line;

• p - print all lines that fell within /PAT1/,/PAT2/ and were not skipped or deleted.