The termios.h header file contains constants, prototypes, and typedef definitions of POSIX terminal I/O functions. It includes the __termcp structure, and declares the following functions:
| cfgetispeed() | cfgetospeed() | cfsetispeed() | cfsetospeed() | tcdrain() |
| tcflow() | tcflush() | tcgetattr() | __tcgetcp() | tcgetsid() |
| tcsendbreak() | tcsetattr() | __tcsetcp() | __tcsettables() |
These functions are supported only in a POSIX program.
The termios.h header file also contains constants, prototypes and typedef definitions for the w_ioctl() function.