v0.40: Create exercises. Challenge the community.

strncat

Your mission

Write gm_strncat, your own strncat, which appends at most n characters from src onto the end of dst, then terminates the result.

See it in action

gm_strncat("git ", "rebase --interactive", 6)

Expected result

git rebase

Your checklist

For your own tracking. Tests grade your code.

Find the end of dst (its current \0) and start writing there.
Copy characters from src until you have appended n of them or reached the end of src, whichever comes first.
Always write a terminating \0 after the appended characters, even when n is 0 or you stopped early.
The gotcha: unlike strncpy, gm_strncat always null-terminates, and n limits how many characters are taken from src, not the total length of the result.
Return dst.

More examples

gm_strncat("docker ", "compose", 64)

Expected result

docker compose

gm_strncat("commit", " --amend", 0)

Expected result

commit

Constraints

Expected files

strncat.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

libc

Standard C library

Implements the contract of a function from the standard C library.

strncat

Writing text without overflowing

Your mission

Write gm_strncat, your own strncat, which appends at most n characters from src onto the end of dst, then terminates the result.

See it in action

gm_strncat("git ", "rebase --interactive", 6)

Expected result

git rebase

Your checklist

For your own tracking. Tests grade your code.

Find the end of dst (its current \0) and start writing there.
Copy characters from src until you have appended n of them or reached the end of src, whichever comes first.
Always write a terminating \0 after the appended characters, even when n is 0 or you stopped early.
The gotcha: unlike strncpy, gm_strncat always null-terminates, and n limits how many characters are taken from src, not the total length of the result.
Return dst.

More examples

gm_strncat("docker ", "compose", 64)

Expected result

docker compose

gm_strncat("commit", " --amend", 0)

Expected result

commit

Constraints

Expected files

strncat.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

libc

Standard C library

Implements the contract of a function from the standard C library.

Tests

Run the tests to grade your code

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

Build

01n smaller than src: truncated but terminatedWaiting

02n larger than src: full appendWaiting

03n is 0: nothing appended, still terminatedWaiting

04Append onto an empty dstWaiting

05n exactly equals src lengthWaiting

06Empty src leaves dst unchangedWaiting

07Truncate src mid-stringWaiting

strncat

Your mission

Write gm_strncat, your own strncat, which appends at most n characters from src onto the end of dst, then terminates the result.

See it in action

gm_strncat("git ", "rebase --interactive", 6)

Expected result

git rebase

Your checklist

For your own tracking. Tests grade your code.

Find the end of dst (its current \0) and start writing there.
Copy characters from src until you have appended n of them or reached the end of src, whichever comes first.
Always write a terminating \0 after the appended characters, even when n is 0 or you stopped early.
The gotcha: unlike strncpy, gm_strncat always null-terminates, and n limits how many characters are taken from src, not the total length of the result.
Return dst.

More examples

gm_strncat("docker ", "compose", 64)

Expected result

docker compose

gm_strncat("commit", " --amend", 0)

Expected result

commit

Constraints

Expected files

strncat.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

libc

Standard C library

Implements the contract of a function from the standard C library.

v0.40: Create exercises. Challenge the community.

Meet Studio →

strncat

Writing text without overflowing

Your mission

Write gm_strncat, your own strncat, which appends at most n characters from src onto the end of dst, then terminates the result.

See it in action

gm_strncat("git ", "rebase --interactive", 6)

Expected result

git rebase

Your checklist

For your own tracking. Tests grade your code.

Find the end of dst (its current \0) and start writing there.
Copy characters from src until you have appended n of them or reached the end of src, whichever comes first.
Always write a terminating \0 after the appended characters, even when n is 0 or you stopped early.
The gotcha: unlike strncpy, gm_strncat always null-terminates, and n limits how many characters are taken from src, not the total length of the result.
Return dst.

More examples

gm_strncat("docker ", "compose", 64)

Expected result

docker compose

gm_strncat("commit", " --amend", 0)

Expected result

commit

Constraints

Expected files

strncat.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

libc

Standard C library

Implements the contract of a function from the standard C library.

Tests

Run the tests to grade your code

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

Build

01n smaller than src: truncated but terminatedWaiting

02n larger than src: full appendWaiting

03n is 0: nothing appended, still terminatedWaiting

04Append onto an empty dstWaiting

05n exactly equals src lengthWaiting

06Empty src leaves dst unchangedWaiting

07Truncate src mid-stringWaiting