GitHub - hiromichinomata/emacro: Use emacs macro like grep

Transform each line of a file with Emacs-style key sequences—useful for quick line-oriented edits in the same way you might use grep for line-oriented filtering.

The macro language supports movement, search, line/word editing, and literal insertion. Processing is one line at a time; the cursor is byte-based (ASCII / UTF-8 multibyte lines are not fully “character-aware” for all operations).

Requirements

Go 1.22 or later

Install

From a clone of this repository:

To install the binary onto your PATH (from the module root):

If the module is published under a full import path (for example github.com/yourname/emacro), you can also use:

go install github.com/yourname/emacro@latest

(after setting the module line in go.mod to match that path).

Usage

emacro <macro> <file> [file...]

Multiple files: read in order; output is the concatenation of each file’s transformed lines (no filename headers).
Standard input: use - as a file name.
Help: emacro -h or emacro --help.

Example

$ cat test/sample.csv
2020-04-01 01:23,user01,male,17
2020-04-01 02:34,user02,female,27
2020-04-01 03:45,user03,male,37

$ grep female test/sample.csv
2020-04-01 02:34,user02,female,27

$ emacro '^S,user^D^D' test/sample.csv
2020-04-01 01:23,user,male,17
2020-04-01 02:34,user,female,27
2020-04-01 03:45,user,male,37

$ cat test/sample.csv | emacro '^S,user^D^D' -
2020-04-01 01:23,user,male,17
2020-04-01 02:34,user,female,27
2020-04-01 03:45,user,male,37

Macro reference

Control (two bytes: `^` + letter)

Sequence	Binding	Effect
`^A`	`C-a`	Move to beginning of line
`^B`	`C-b`	Move backward one character
`^D`	`C-d`	Delete character under cursor (or one before end of line)
`^E`	`C-e`	Move to end of line
`^F`	`C-f`	Move forward one character
`^K`	`C-k`	Kill line: delete from cursor through end of line
`^N`	`C-n`	No-op (each line is processed separately)
`^S`	`C-s`	Forward search: move cursor past the next match (see below)
`^R`	`C-r`	Backward search: move cursor to the start of the last match before the current position (see below)
`^^`	—	Insert a literal `^`

Any other character is inserted at the cursor; the cursor advances one byte.

Search terms (`^S` / `^R`)

The search string begins after ^S or ^R and ends at the next ^ in the macro, or at end of macro. To avoid swallowing the rest of the macro (for example before inserting text), terminate the term with a harmless command such as ^N before further letters—e.g. ^E^R,user^NX if you need a literal X after a ^R,user search.

If the search fails, the engine only advances the macro by one step (same idea as the original ^S behavior), so the following bytes may be interpreted differently than after a successful search.

Meta (three bytes: `^` + `m` + letter)

Sequence	Binding	Effect
`^mf`	`M-f`	Forward one word
`^mb`	`M-b`	Backward one word
`^md`	`M-d`	Kill forward from cursor through end of next word

A word is a maximal run of ASCII letters, digits, or _.

Notes

Unknown two-byte sequences like ^Z advance by one byte in the macro stream (the ^ is skipped in that step).
Multibyte UTF-8 characters are easiest to reason about when lines stay ASCII; byte indexing can split Unicode code points.

Development

CI runs go test on push and pull request (.github/workflows/ci.yml).