2 unstable releases

0.1.0 Jan 6, 2022
0.0.1 Dec 29, 2021

#1276 in Command line utilities



fnr – find and replace

Like find ... | xargs sed ..., but with a memorable interface.

Recursively find and replace patterns in files and directories.



fnr is intended to be more intuitive to use than sed, but is not a drop in replacement. Instead, it's focused on making bulk changes in a directory, and is more comparable with your IDE or editor's find and replace tool.

fnr is alpha quality. Don't use --write in situations you wouldn't be able to revert.


Replace "old_function" with "new_function" in current directory.

fnr old_function new_function

Choose files and directories to consider.

fnr 'EDITOR=vim' 'EDITOR=emacs' ~/.zshrc ~/.config/

We can use --literal so the pattern isn't treated as a regular expression.

fnr --literal 'i += 1' 'i++'

Replace using capturing groups.

fnr 'const (\w+) = \d+;' 'const $1 = 42;'

Use -W --write to write changes back to files.

fnr --write 'Linus Torvalds' 'Linux Torvalds'

Use -I --include to only modify files or directories matching a pattern.

fnr --include 'Test.*\.kt' 'mockito' 'mockk'

Similarly, use -E --exclude to ignore certain files.

fnr --exclude ChangeLog 2021 2022

Files and directories to consider can also be given over standard input.

find /tmp/ -name "*.csv" -print | fnr "," "\t"

Use -p --prompt to individually accept or reject each replacement.

fnr --prompt --literal 'i++' '++i'
--- ./README.md: 2 matching lines
-   18: $ fnr --literal 'i += 1' 'i++'
+   18: $ fnr --literal 'i += 1' '++i'
Stage this replacement [y,n,q,a,e,d,?] ?


cargo install fnr

If you'd prefer to build from source instead:

$ git clone git@github.com/erik/fnr.git
$ cd fnr
$ cargo install --path .


Built on top of ripgrep's path traversal and pattern matching, so even though performance isn't an explicit goal, it's not going to be the bottleneck.

In fact, without writing changes back to files, it's imperceptibly slower than ripgrep itself.

Command Mean [ms] Min [ms] Max [ms] Relative
rg "EINVAL" ./linux 510.4 ± 25.8 467.6 555.0 1.00
fnr "EINVAL" "ERR_INVALID" ./linux 620.4 ± 22.1 573.7 649.7 1.22 ± 0.08
fnr --write "EINVAL" "ERR_INVALID" ./linux 3629.0 ± 76.2 3538.0 3802.3 7.11 ± 0.39
ag "EINVAL" ./linux 2560.0 ± 43.6 2518.4 2668.1 5.02 ± 0.27
grep -irI "EINVAL" ./linux 37215.8 ± 7444.7 31316.1 49096.6 72.92 ± 15.04

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