v0.40: Create exercises. Challenge the community.

line_reader_repair

Your mission

Implement read_next_line, a function that reads the next text line from a file descriptor.

See it in action

read_next_line(fd) on a file containing `red\nblue`

Expected result

`red\n`, then `blue`, then `NULL`

Your checklist

For your own tracking. Tests grade your code.

Create line_reader.c and line_reader.h.
Expose the function char *read_next_line(int fd); from the header.
Each successful call returns a newly allocated string containing the next line from fd.
Keep the trailing newline in the returned string when the line has one.
As soon as a newline has been read, return that line without waiting for end of file.
At end of file, return the remaining text if any, then return NULL on later calls.
Return NULL on read errors, invalid descriptors, or when no more text is available.
The grading build defines READ_CHUNK_SIZE; use it as the maximum byte count for each read call.
Do not leave internal buffers allocated after the descriptor reaches end of file.

More examples

read_next_line(fd) on an empty file

Expected result

NULL

Constraints

Expected files

line_reader.cline_reader.h

Allowed functions

readmallocfree

Allowed headers

<stdlib.h>declares malloc and free

<unistd.h>declares read

line_reader_repair

Files and streams

Your mission

Implement read_next_line, a function that reads the next text line from a file descriptor.

See it in action

read_next_line(fd) on a file containing `red\nblue`

Expected result

`red\n`, then `blue`, then `NULL`

Your checklist

For your own tracking. Tests grade your code.

Create line_reader.c and line_reader.h.
Expose the function char *read_next_line(int fd); from the header.
Each successful call returns a newly allocated string containing the next line from fd.
Keep the trailing newline in the returned string when the line has one.
As soon as a newline has been read, return that line without waiting for end of file.
At end of file, return the remaining text if any, then return NULL on later calls.
Return NULL on read errors, invalid descriptors, or when no more text is available.
The grading build defines READ_CHUNK_SIZE; use it as the maximum byte count for each read call.
Do not leave internal buffers allocated after the descriptor reaches end of file.

More examples

read_next_line(fd) on an empty file

Expected result

NULL

Constraints

Expected files

line_reader.cline_reader.h

Allowed functions

readmallocfree

Allowed headers

<stdlib.h>declares malloc and free

<unistd.h>declares read

Tests

Run the tests to grade your code

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

Build

01Returns as soon as a newline is availableWaiting

02Several lines with final textWaiting

03Empty lines stay visibleWaiting

04Single newlineWaiting

05Line longer than the read chunkWaiting

06Empty fileWaiting

07Invalid descriptorWaiting

line_reader_repair

Your mission

Implement read_next_line, a function that reads the next text line from a file descriptor.

See it in action

read_next_line(fd) on a file containing `red\nblue`

Expected result

`red\n`, then `blue`, then `NULL`

Your checklist

For your own tracking. Tests grade your code.

Create line_reader.c and line_reader.h.
Expose the function char *read_next_line(int fd); from the header.
Each successful call returns a newly allocated string containing the next line from fd.
Keep the trailing newline in the returned string when the line has one.
As soon as a newline has been read, return that line without waiting for end of file.
At end of file, return the remaining text if any, then return NULL on later calls.
Return NULL on read errors, invalid descriptors, or when no more text is available.
The grading build defines READ_CHUNK_SIZE; use it as the maximum byte count for each read call.
Do not leave internal buffers allocated after the descriptor reaches end of file.

More examples

read_next_line(fd) on an empty file

Expected result

NULL

Constraints

Expected files

line_reader.cline_reader.h

Allowed functions

readmallocfree

Allowed headers

<stdlib.h>declares malloc and free

<unistd.h>declares read

v0.40: Create exercises. Challenge the community.

Meet Studio →

line_reader_repair

Files and streams

Your mission

Implement read_next_line, a function that reads the next text line from a file descriptor.

See it in action

read_next_line(fd) on a file containing `red\nblue`

Expected result

`red\n`, then `blue`, then `NULL`

Your checklist

For your own tracking. Tests grade your code.

Create line_reader.c and line_reader.h.
Expose the function char *read_next_line(int fd); from the header.
Each successful call returns a newly allocated string containing the next line from fd.
Keep the trailing newline in the returned string when the line has one.
As soon as a newline has been read, return that line without waiting for end of file.
At end of file, return the remaining text if any, then return NULL on later calls.
Return NULL on read errors, invalid descriptors, or when no more text is available.
The grading build defines READ_CHUNK_SIZE; use it as the maximum byte count for each read call.
Do not leave internal buffers allocated after the descriptor reaches end of file.

More examples

read_next_line(fd) on an empty file

Expected result

NULL

Constraints

Expected files

line_reader.cline_reader.h

Allowed functions

readmallocfree

Allowed headers

<stdlib.h>declares malloc and free

<unistd.h>declares read

Tests

Run the tests to grade your code

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

Build

01Returns as soon as a newline is availableWaiting

02Several lines with final textWaiting

03Empty lines stay visibleWaiting

04Single newlineWaiting

05Line longer than the read chunkWaiting

06Empty fileWaiting

07Invalid descriptorWaiting