How to change text in other line when the pattern is found?

Question

I've got this 4-line content:

foo
baa
baz
quz

and I'd like to replace baa to bar only when quz is found.

I've tried these commands (which highlights baa correctly, but says it's not found):

:/quz/s/baa/bar/
:/quz/1,$s@baa@bar@

E486: Pattern not found: baa

and this:

:/quz/%s/baa/bar/
:/baa/,/quz/%s/baa/bar/

E488: Trailing characters

and this:

/quz/s/baa/bar/
/quz/%s/baa/bar/

search hit BOTTOM, continuing at TOP

What I am doing wrong? What is the correct syntax?

Answer 1

:/baa/,/quz/s/baa/bar/ works, but that will only work with the first occurrence of baa. If you want to replace all occurrences of baa with bar that come before quz:

,/quz/s/baa/bar

If your scenario calls for replacing all occurrences of baa if quz is found:

 /quz/,%s/baa/bar

That will replace all occurrences of baa with bar if quz is found. This is basically using the range /quz/,1,$ which is permitted (% is equivalent to 1,$).

From :h cmdline-ranges

If more line specifiers are given than required for the command, the first one(s) will be ignored.

So if the first line specifier /quz/ fails, it generates an error and causes the rest of the command to not execute. But, if it does find a match, the 1,$ range is used since substitution only needs 2 range specifiers.

Conditional substitution

If you want to conditionally replace baa with bar, you'll want to use the :global command.

---

If you want replace baa with bar if it comes before quz:

:g/quz/?baa?,s//bar

Explanation:

g/quz/   - Moves to the next 'quz'
?baa?,   - Create a range from the last 'baa' to the current line
s//bar   - Reuse the previous pattern (baa) and substitute with 'bar'

However, that only matches the first baa that comes before quz.

---

If you want to replace all occurrences of baa that comes before quz:

g/quz/?quz\|\%^?,s/baa/bar

Explanation:

g/quz/       - Moves to the next 'quz'
?quz\|\%^?,  - Create a range from the previous 'quz' or the
               beginning of the buffer.
s/baa/bar    - Replace 'baa' with 'bar'

---

If you want to replace all occurrences of baa with bar if they're between two quz lines:

g/quz/silent! ??,s/baa/bar

Explanation:

g/quz/      - Moves to the next 'quz'
silent!     - The first occurence of 'quz' won't have a previous
              'quz' match. So, ignore the error about an invalid
              range.
??,         - Reuse 'quz' pattern to search for the previous occurrence
s/baa/bar   - Replace 'baa' with 'bar'

Answer 2

Ok, it was very close and this actually worked:

:/baa/,/quz/s/baa/bar/