sd - s[earch] & d[isplace]

sd is an intuitive find & replace CLI.

The Pitch

Why use it over any existing tools?

Painless regular expressions

sd uses regex syntax that you already know from JavaScript and Python. Forget about dealing with quirks of sed or awk - get productive immediately.

String-literal mode

Non-regex find & replace. No more backslashes or remembering which characters are special and need to be escaped.

Easy to read, easy to write

Find & replace expressions are split up, which makes them easy to read and write. No more messing with unclosed and escaped slashes.

Smart, common-sense defaults

Smart-cased regular expressions also come with a sane syntax that's not opt-in. Defaults follow common sense and are tailored for typical daily use.

Comparison to sed

While sed does a whole lot more, sd focuses on doing just one thing and doing it well.

Some cherry-picked examples, where sd shines:

• Simpler syntax for replacing all occurrences:
  • sd: sd before after
  • sed: sed s/before/after/g
• Replace newlines with commas:
  • sd: sd '\n' ','
  • sed: sed ':a;N;$!ba;s/\n/,/g'
• Extracting stuff out of strings containing slashes:
  • sd: echo "sample with /path/" | sd '.*(/.*/)' '$1'
  • sed: use different delimiters every time depending on expression so that the command is not completely unreadable
    • echo "sample with /path/" | sed -E 's/.*(/.*/)/\1/g'
    • echo "sample with /path/" | sed -E 's|.*(/.*/)|\1|g'
• In place modification of files:
  • sd: sd -i before after file.txt
  • sed: you need to remember to use -e or else some platforms will consider the next argument to be a backup suffix
    • sed -i -e 's/before/after/g' file.txt

Benchmarks

Simple replacement on ~1.5 gigabytes of JSON

hyperfine -w 3 'sed -E "s/\"/\'/g" *.json >/dev/null' 'sd "\"" "\'" *.json >/dev/null' --export-markdown out.md

Command	Mean [s]	Min…Max [s]
sed -E "s/\"/'/g" *.json >/dev/null	2.338 ± 0.008	2.332…2.358
sed "s/\"/'/g" *.json >/dev/null	2.365 ± 0.009	2.351…2.378
sd "\"" "'" *.json >/dev/null	0.997 ± 0.006	0.987…1.007

Result: ~2.35 times faster

Regex replacement on a ~55M json file:

hyperfine \
'sed -E "s:(\w+):\1\1:g" dump.json >/dev/null'\
"sed 's:\(\w\+\):\1\1:g' dump.json >/dev/null"\
'sd "(\w+)" "$1$1" dump.json >/dev/null'

Command	Mean [s]	Min…Max [s]
sed -E "s:(\w+):\1\1:g" dump.json >/dev/null	11.315 ± 0.215	11.102…11.725
sed 's:\(\w\+\):\1\1:g' dump.json >/dev/null	11.239 ± 0.208	11.057…11.762
sd "(\w+)" "$1$1" dump.json >/dev/null	0.942 ± 0.004	0.936…0.951

Result: ~11.93 times faster

Installation

Cargo

cargo install sd

Arch Linux

AUR package for sd.

Quick Guide

1. String-literal mode. By default, expressions are treated as regex. Use -s or --string-mode to disable regex.

> echo 'lots((([]))) of special chars' | sd -s '((([])))' ''
lots of special chars

2. Basic regex use - let's trim some trailing whitespace

> echo 'lorem ipsum 23   ' | sd '\s+$' ''
lorem ipsum 23

3. Capture groups

Indexed capture groups:

> echo 'cargo +nightly watch' | sd '(\w+)\s+\+(\w+)\s+(\w+)' 'cmd: $1, channel: $2, subcmd: $3'
cmd: cargo, channel: nightly, subcmd: watch

Named capture groups:

> echo "123.45" | sd '(?P<dollars>\d+)\.(?P<cents>\d+)' '$dollars dollars and $cents cents'
123 dollars and 45 cents

In the unlikely case you stumble upon ambiguities, resolve them by using ${var} instead of $var. Here's an example:

> echo '123.45' | sd '(?P<dollars>\d+)\.(?P<cents>\d+)' '$dollars_dollars and $cents_cents'
 and 
> echo '123.45' | sd '(?P<dollars>\d+)\.(?P<cents>\d+)' '${dollars}_dollars and ${cents}_cents'
123_dollars and 45_cents

4. Find & replace in a file

> sd -i 'window.fetch' 'fetch' http.js

That's it. The file is modified in-place.

To do a dry run:

> sd 'window.fetch' 'fetch' http.js 

5. Find & replace across project

Good ol' unix philosophy to the rescue.

sd -i 'from "react"' 'from "preact"' $(fd -t f)

Same, but with backups (consider version control).

for file in $(fd -t f); do
  cp "$file" "$file.bk"
  sd -i 'from "react"' 'from "preact"' "$file"; 
done