- open, close, read, write
- lseek, create, fcntl, ioctl
- fopen, fclose, fread, fwrite
- fgetc, fputc, fgets, fputs
- fscanf, fprintf, sscanf, sprintf
- fseek, ftell, rewind
- ungetc, ferror, feof, fflush
- stat, fstat, lstat
- umask
- chmod, fchmod
- chown, fchown, lchown
- link, symlink
- remove, rename
- mkdir, rmdir
- opendir, closedir, readdir, rewinddir
- chdir, fchdir
- sync, fsync
- getcwd
- getpid, getppid, getuid, geteuid, getgid, getegid
- fork
- exit, atexit
- wait, waitpid
- execel, execv, execle, execve, execlp, execvp
- system
- pthread_create, pthread_exit, pthread_join
- signal
- kill, raise
- sleep, alarm, pause
- pthread_cancel
- pthread_setcancelstate, pthread_setcalceltype
- Pipe: pipe, read, write, close
- FIFO: mkfifo, open, read, write, close
- Message queue: msgget, msgctl, msgsnd, msgrcv
- Shared memory: shmget, shmctl, shmat, shmdt
- Memory-mapped file: mmap, munmap
- System V semaphore : semget, semctl, semop
- POSIX semaphore : sem_init, sem_wait, sem_trywait, sem_post, setm_getvalue, sem_destroy
- Mutex : pthread_mutex_init, pthread_mutex_destroy, pthread_mutex_lock, pthread_mutex_trylock, pthread_mutex_unlock
- Condition variables : pthread_cond_init, pthread_cond_destroy, pthread_cond_wait, pthread_cond_signal, pthread_cond_breadcast
- TCP server : socket, bind, listen, accept, read, write, close
- TCP client : socket, connect, read, write, close
- UDP server : socket, bind, recvfrom, sendto, close
- UDP client : socket, sendto, recvfrom, close