system-programming/03_BufferedIO

Chapter 3 – Buffered I/O

Difference Between Byte-Level and Buffered I/O

• System calls like read() and write() operate at a low level: each call may result in direct disk access.
• C libraries use buffered I/O (fread(), fwrite(), fprintf()), accumulating data in memory to reduce system calls.

Buffered I/O API

• Uses FILE * type from <stdio.h>.
• Functions:
  • fopen(), fclose(): open/close file.
  • fread(), fwrite(): binary I/O.
  • fprintf(), fscanf(), fgets(), fputs(): formatted or text I/O.

Types of Buffering

• Fully buffered: flush when buffer is full.
• Line buffered: flush at end of line (e.g., terminals).
• Unbuffered: no accumulation (e.g., stderr).

Buffer Management

• setvbuf() or setbuf() allows custom buffering.
• Useful for optimizing performance or interactive environments.

When to Use Buffered I/O

• When performance matters and immediate file system synchronization isn't required.
• For formatted I/O, the C library offers more simplicity and readability.