vrk recase

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vrk, compiled to WebAssembly

# Converts snake_case to camelCase.

Command to run

echo 'user_first_name' | vrk recase --to camel

Enter runs, Shift+Enter adds a line

output

Press RUN. Nothing leaves your browser.

files you can cat:

Edit the command and press RUN. Open the full playground for more recipes, or install vrk to run it on your own files.

vrk recase converts text between naming conventions such as snake_case, camelCase, kebab-case, and PascalCase.

The problem

Converting 200 field names from snake_case to camelCase takes 30 lines of Python to handle edge cases: leading underscores, consecutive capitals, numeric suffixes. sed 's/_\(.\)/\U\1/g' handles simple cases but breaks on acronyms like http_api_url.

The solution

vrk recase converts between naming conventions: snake_case, camelCase, PascalCase, kebab-case, SCREAMING_SNAKE, Title Case, and more. It detects the input convention and handles acronyms. It converts line by line, so you can convert a batch.

Before and after

Before

echo 'user_first_name' | sed 's/_\(.\)/\U\1/g'
# Breaks on acronyms, doesn't handle PascalCase or kebab-case

After

echo 'user_first_name' | vrk recase --to camel

Example

echo 'user_first_name' | vrk recase --to camel

Exit codes

Code	Meaning
0	Success
1	Runtime error (I/O failure)
2	–to missing or invalid value, interactive TTY with no stdin

Flags

Flag	Short	Type	Description
`--to`		string	Target convention: camel, pascal, snake, kebab, screaming, title, lower, upper
`--json`	-j	bool	Emit JSON per line: {input, output, from, to}
`--quiet`	-q	bool	Suppress stderr output

Supported conventions

vrk recase converts identifiers between naming conventions such as camelCase, snake_case and kebab-case.

Convention	Example	Flag value
camelCase	`helloWorld`	`camel`
PascalCase	`HelloWorld`	`pascal`
snake_case	`hello_world`	`snake`
kebab-case	`hello-world`	`kebab`
SCREAMING_SNAKE	`HELLO_WORLD`	`screaming`
Title Case	`Hello World`	`title`
lowercase	`hello world`	`lower`
UPPERCASE	`HELLO WORLD`	`upper`

recase detects the input convention itself. You only set the target with --to.

How it works

$ echo 'hello_world' | vrk recase --to camel
helloWorld

$ echo 'helloWorld' | vrk recase --to snake
hello_world

$ echo 'user_first_name' | vrk recase --to pascal
UserFirstName

$ echo 'UserFirstName' | vrk recase --to kebab
user-first-name

Batch conversion

recase converts each line on its own, so you can convert many names at once:

$ printf 'user_first_name\nuser_last_name\nemail_address\n' | vrk recase --to camel
userFirstName
userLastName
emailAddress

JSON output

$ echo 'hello_world' | vrk recase --to camel --json
{"from":"snake","input":"hello_world","output":"helloWorld","to":"camel"}

Pipeline integration

Convert API field names

# Extract keys from a JSON object and convert to camelCase
echo '{"user_name":"alice","email_addr":"[email protected]"}' | \
  jq -r 'keys[]' | vrk recase --to camel

Rename files in a directory

# Convert kebab-case filenames to snake_case
for f in *.md; do
  NEWNAME=$(echo "${f%.md}" | vrk recase --to snake).md
  mv "$f" "$NEWNAME"
done

When it fails

If you leave out --to, recase exits 2:

$ echo 'hello' | vrk recase
usage error: --to is required
$ echo $?
2

If the convention is unknown, recase exits 2:

$ echo 'hello' | vrk recase --to unknown
usage error: recase: unknown convention: "unknown"; valid: camel, pascal, snake, kebab, screaming, title, lower, upper
$ echo $?
2