v0.40: Create exercises. Challenge the community.

snake_fmt

Your mission

Write a program that reads one camelCase identifier from the command line and prints it reformatted as snake_case.

See it in action

./snake_fmt "buildReactApp"

Expected result

build_react_app

Your checklist

For your own tracking. Tests grade your code.

Accept exactly one argument after the binary name.
Scan every character of that argument: whenever an uppercase letter is found, emit an underscore followed by the lowercase version of that letter.
All other characters are printed unchanged.
Always finish the output with a newline.
If the program does not receive exactly one argument (argc must be 2), print wrong number of arguments followed by a newline and exit.

More examples

./snake_fmt "vibeCodingMetGccToday" | cat -e

Expected result

vibe_coding_met_gcc_today$

./snake_fmt | cat -e

Expected result

wrong number of arguments$

Constraints

Expected files

snake_fmt.c

Allowed functions

write

snake_fmt

Transforming text

Your mission

Write a program that reads one camelCase identifier from the command line and prints it reformatted as snake_case.

See it in action

./snake_fmt "buildReactApp"

Expected result

build_react_app

Your checklist

For your own tracking. Tests grade your code.

Accept exactly one argument after the binary name.
Scan every character of that argument: whenever an uppercase letter is found, emit an underscore followed by the lowercase version of that letter.
All other characters are printed unchanged.
Always finish the output with a newline.
If the program does not receive exactly one argument (argc must be 2), print wrong number of arguments followed by a newline and exit.

More examples

./snake_fmt "vibeCodingMetGccToday" | cat -e

Expected result

vibe_coding_met_gcc_today$

./snake_fmt | cat -e

Expected result

wrong number of arguments$

Constraints

Expected files

snake_fmt.c

Allowed functions

write

Tests

Run the tests to grade your code

Build your code, then check each test here. Open a result to inspect its output.

Build

01No argumentsWaiting

02Empty stringWaiting

03Three-segment identifierWaiting

04Dev-culture phraseWaiting

05Too many argumentsWaiting

06Single lowercase characterWaiting

snake_fmt

Your mission

Write a program that reads one camelCase identifier from the command line and prints it reformatted as snake_case.

See it in action

./snake_fmt "buildReactApp"

Expected result

build_react_app

Your checklist

For your own tracking. Tests grade your code.

Accept exactly one argument after the binary name.
Scan every character of that argument: whenever an uppercase letter is found, emit an underscore followed by the lowercase version of that letter.
All other characters are printed unchanged.
Always finish the output with a newline.
If the program does not receive exactly one argument (argc must be 2), print wrong number of arguments followed by a newline and exit.

More examples

./snake_fmt "vibeCodingMetGccToday" | cat -e

Expected result

vibe_coding_met_gcc_today$

./snake_fmt | cat -e

Expected result

wrong number of arguments$

Constraints

Expected files

snake_fmt.c

Allowed functions

write

snake_fmt

Transforming text

Your mission

Write a program that reads one camelCase identifier from the command line and prints it reformatted as snake_case.

See it in action

./snake_fmt "buildReactApp"

Expected result

build_react_app

Your checklist

For your own tracking. Tests grade your code.

Accept exactly one argument after the binary name.
Scan every character of that argument: whenever an uppercase letter is found, emit an underscore followed by the lowercase version of that letter.
All other characters are printed unchanged.
Always finish the output with a newline.
If the program does not receive exactly one argument (argc must be 2), print wrong number of arguments followed by a newline and exit.

More examples

./snake_fmt "vibeCodingMetGccToday" | cat -e

Expected result

vibe_coding_met_gcc_today$

./snake_fmt | cat -e

Expected result

wrong number of arguments$

Constraints

Expected files

snake_fmt.c

Allowed functions

write

Tests

Run the tests to grade your code

Build your code, then check each test here. Open a result to inspect its output.

Build

01No argumentsWaiting

02Empty stringWaiting

03Three-segment identifierWaiting

04Dev-culture phraseWaiting

05Too many argumentsWaiting

06Single lowercase characterWaiting

v0.40: Create exercises. Challenge the community.

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