A shell's > on addr no longer resets it, so echo /re/ > addr searches on

Truncating addr reset it to #0, so a shell's find-and-replace loop matched the first hit for ever, .+#1 read 1 1 each time, and foo x foo y foo became foobarbarbar... acme resets addr on the first open (xfid.c:105-108), for clients that hold the fid; a shell cannot. Here neither an open nor a truncation resets it: the address written is evaluated from the last one, and 0 or , starts over. Documented as a departure from acme.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 11 insertions, 3 deletions

diff --git a/docs/fs.md b/docs/fs.md
index b8425d2f..7ccb9a91 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -369,8 +369,16 @@ leaves `addr` just past what it wrote, so a second `echo x > data` deletes
 the empty range there and inserts after the first rather than replacing it
 again; write `addr` before each replacement.
 `addr` belongs to the pane rather than to a client and keeps what was written
-until someone writes or truncates it, so writing an address and reading it
-back evaluates it, which is what acme(4) promises of its own `addr`.
+until someone writes another, so writing an address and reading it back
+evaluates it, which is what acme(4) promises of its own `addr`. Unlike acme,
+neither an open nor a truncation resets it: acme sets it to `#0` when the
+first client opens `addr` (editors/acme/xfid.c:105-108), which suits a
+client that holds the fid, but a shell opens the file anew for every
+`echo /re/ > addr` and so would search from the top each time and never
+advance. Here each such write searches on from the last address, as `>>`
+does; write `0` to start again from the top. A search wraps at the end of
+the text, so a find-all loop stops when the address comes back to where it
+began, or bounds itself with `limit`.
 
 The regular expressions are mvzr's (sets, `\d`/`\w`/`\s`, `{m,n}` and
 lazy `*?` included), searched the way sam searches (editors/acme/regx.c): as
@@ -409,7 +417,7 @@ expression`, `regular expression search gave up, ...`, or sam's
 `addresses out of order` for a range that ends before it starts
 (`#100,#50`), which acme lets through. A failed write to `addr` leaves no
 address at all, where acme
-keeps the old one: until an address is written or `addr` is truncated,
+keeps the old one: until a good address is written,
 reading `addr`, and reading, writing or truncating `data` and `xdata`, fail
 with `no address: the last one written to addr failed`, so a script that
 missed its target cannot then write at the last one.