Live Action Search and Replace (LASR)

When performing a global search-and-replace using e.g. sed, it can be difficult to hone in on the exact correct pattern. lasr makes this easier by showing live results as you type.

Installation

Binary artifacts can be downloaded from the releases page.

If you have a rust toolchain, you can install from source:

cargo install lasr

Usage

Simply run lasr to start a search-and-replace in the current directory. You may run lasr <path> [<path>...] to search a specific directories or files. This will open a TUI where you can start typing a search pattern and see live matches below. Once you are happy with the search pattern, press Tab to start editing the replacement pattern. Finally, press Enter to confirm and execute the replacement, or Esc to cancel the replacement. You can press Ctrl+S to toggle case-insensitive searching, or pass the -i flag to enable case-insensitive search on startup.

Syntax

The pattern syntax is based on the rust regex crate. The replacement syntax is based on the replace method in that crate.

Replacements may reference numbered groups as $1 or ${1}, or named groups like $foo or ${foo}. The {} brackets may be necessary to separate the replacement from other text. $0 or ${0} refers to the entire match.

lasr also supports ast-grep, to search and replace code structurally rather than matching text with a regex. If your search pattern contains an uppercase replacement like $FN or $$$ARGS, lasr will interpret it as an ast-grep pattern instead of a regex. For example, the pattern $FN($$$ARGS) matches a function call with any number of arguments. The replacement $FN($$$ARGS, "foo") would add a "foo" argument to every matched function call.

You can read more about ast-grep syntax in the ast-grep docs.

Configuration

The configuration file is located at $XDG_CONFIG_HOME/lasr/lasr.toml (~/.config/lasr/lasr.toml by default). The current configuration can be printed by running lasr --dump-config. This can be used as a starting point to edit your own configuration:

lasr --dump-config > ~/.config/lasr/lasr.toml

Default Config

[theme.base]
fg = "Reset"

[theme.find]
fg = "Red"
add_modifier = "CROSSED_OUT"

[theme.replace]
fg = "Green"
add_modifier = "BOLD"

[keys]
c-b = "cursor_left"
c-s = "toggle_ignore_case"
tab = "toggle_search_replace"
left = "cursor_left"
home = "cursor_home"
c-e = "cursor_end"
c-d = "delete_char"
right = "cursor_right"
c-h = "delete_char_backward"
enter = "confirm"
backspace = "delete_char_backward"
c-k = "delete_to_end_of_line"
c-a = "cursor_home"
end = "cursor_end"
c-f = "cursor_right"
c-c = "exit"
esc = "exit"
c-u = "delete_line"
c-w = "delete_word"

General Config

The following settings may be placed at the top-level of the config, not under any section:

Key	Description	Default
threads	Threads to use, 0 to auto-select	0
auto_pairs	Auto-insert matching pairs of ({[	true

Theme Config

The theme section of the config includes 3 "style" sub-sections:

Key	Description
base	Most text/UI
find	Text matched by the pattern
replace	Replacement text

A "style" has the following attributes

Key	Description
fg	Foreground color
bg	Background color
add_modifier	Add modifiers
sub_modifier	Remove modifiers

A color can be an ANSI color name like "red", an ANSI 8-bit color index like "7", or a hex string like "#00FF00".

add_modifier and sub_modifier can be one of the following:

• "BOLD"
• "DIM"
• "ITALIC"
• "UNDERLINED"
• "SLOW_BLINK"
• "RAPID_BLINK"
• "REVERSED"
• "HIDDEN"
• "CROSSED_OUT"

Keys Config

The keys section specifies key bindings. Each key is a single character or key name, optionally followed by "c-" and/or "a-" to specify a ctrl or alt modifier. The following are valid key names:

• a-z, 0-9
• f0-f12
• backspace
• enter
• left
• right
• up
• down
• home
• end
• pageup
• pagedown
• tab
• backtab
• delete
• insert
• esc

Each value in the keys section is one of the following actions:

Action	Description	Default Key Binding
noop	Do nothing, used to unbind a default key
exit	Exit without performing any replacement	Esc, Ctrl+C
confirm	Exit and perform replacements	Enter
toggle_search_replace	Switch focus between the "search" and "replace" inputs	Tab
toggle_ignore_case	Toggle ignore case flag	Ctrl+S
cursor_left	Move cursor left one character	←, Ctrl+B
cursor_right	Move cursor right one character	→, Ctrl+F
cursor_home	Move cursor to beginning of line	Home, Ctrl+A
cursor_end	Move cursor to end of line	End, Ctrl+E
delete_char	Delete character at cursor position	Ctrl+D
delete_char_backward	Delete character before cursor (backspace)	Backspace, Ctrl+H
delete_word	Delete word before cursor	Ctrl+W
delete_to_end_of_line	Delete from cursor to end of line	Ctrl+K
delete_line	Delete entire line	Ctrl+U

Troubleshooting

Logs are located at $XDG_CACHE_HOME/lasr/log.txt. Log verbosity can be increased by setting the environment variable RUST_LOG to debug or trace. See env_logger for more info.

Similar

serpl and scooter are both "live" TUI search/replace tools similar to lasr. The main difference is that lasr focuses on showing results for multiple files "live" as you type, while serpl and scooter require changing focus to scroll through file results.

sad is an interactive search and replace tool. It allows you to approve/reject each replacement, but must be re-run each time you change the pattern.

sd provides a simpler CLI alternative to sed, but is not interactive.