|TCGETATTR(3P)||POSIX Programmer's Manual||TCGETATTR(3P)|
int tcgetattr(int fildes, struct termios *termios_p);
The termios_p argument is a pointer to a termios structure.
The tcgetattr() operation is allowed from any process.
If the terminal device supports different input and output baud rates, the baud rates stored in the termios structure returned by tcgetattr() shall reflect the actual baud rates, even if they are equal. If differing baud rates are not supported, the rate returned as the output baud rate shall be the actual baud rate. If the terminal device does not support split baud rates, the input baud rate stored in the termios structure shall be the output rate (as one of the symbolic values).
- The fildes argument is not a valid file descriptor.
- The file associated with fildes is not a terminal.
The following sections are informative.
A program that uses these functions should be written to catch all signals and take other appropriate actions to ensure that when the program terminates, whether planned or not, the terminal device's state is restored to its original state.
Existing practice dealing with error returns when only part of a request can be honored is based on calls to the ioctl() function. In historical BSD and System V implementations, the corresponding ioctl() returns zero if the requested actions were semantically correct, even if some of the requested changes could not be made. Many existing applications assume this behavior and would no longer work correctly if the return value were changed from zero to -1 in this case.
Note that either specification has a problem. When zero is returned, it implies everything succeeded even if some of the changes were not made. When -1 is returned, it implies everything failed even though some of the changes were made.
Applications that need all of the requested changes made to work properly should follow tcsetattr() with a call to tcgetattr() and compare the appropriate field values.
The Base Definitions volume of POSIX.1‐2017, Chapter 11, General Terminal Interface, <termios.h>
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|2017||IEEE/The Open Group|