GNU C Library (glibc)

1. Memory allocation

   malloc, free, obstacks and memory mapping.

2. Input and output overview

   Streams versus file descriptors, stdio buffering and file position.

3. Low-level I/O

   open, read, write, lseek, poll and select on file descriptors.

4. Processes

   fork, exec, wait and process control.

5. Signal handling

   sigaction, signal masks, blocking and async-signal-safe handlers.

6. Sockets

   socket, bind, connect, getaddrinfo and name resolution.

7. Error reporting

   errno, strerror, perror and error handling conventions.

8. Date and time

   time, clock_gettime, strftime and time zones.

9. Threads

   Non-POSIX thread extensions in glibc.

10. Tunables

    GLIBC_TUNABLES for tuning malloc, threading and the dynamic loader at runtime.

11. glibc wiki

    Developer wiki and release notes.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.