int tcsetattr(int fildes, int optional_actions,
const struct termios *termios_p);
The tcsetattr() function shall set the parameters associated with the terminal referred to by the open file descriptor fildes (an open file descriptor associated with a terminal) from the termios structure referenced by termios_p as follows:
If the output baud rate stored in the termios structure pointed to by termios_p is the zero baud rate, B0, the modem control lines shall no longer be asserted. Normally, this shall disconnect the line.
If the input baud rate stored in the termios structure pointed to by termios_p is 0, the input baud rate given to the hardware is the same as the output baud rate stored in the termios structure.
The tcsetattr() function shall return successfully if it was able to perform any of the requested actions, even if some of the requested actions could not be performed. It shall set all the attributes that the implementation supports as requested and leave all the attributes not supported by the implementation unchanged. If no part of the request can be honored, it shall return -1 and set errno to [EINVAL]. If the input and output baud rates differ and are a combination that is not supported, neither baud rate shall be changed. A subsequent call to tcgetattr() shall return the actual state of the terminal device (reflecting both the changes made and not made in the previous tcsetattr() call). The tcsetattr() function shall not change the values found in the termios structure under any circumstances.
The effect of tcsetattr() is undefined if the value of the termios structure pointed to by termios_p was not derived from the result of a call to tcgetattr() on fildes; an application should modify only fields and flags defined by this volume of IEEE Std 1003.1-2001 between the call to tcgetattr() and tcsetattr(), leaving all other fields and flags unmodified.
No actions defined by this volume of IEEE Std 1003.1-2001, other than a call to tcsetattr() or a close of the last file descriptor in the system associated with this terminal device, shall cause any of the terminal attributes defined by this volume of IEEE Std 1003.1-2001 to change.
If tcsetattr() is called from a process which is a member of a background process group on a fildes associated with its controlling terminal:
Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno set to indicate the error.
The tcsetattr() function shall fail if:
The tcsetattr() function may fail if:
The following sections are informative.
If trying to change baud rates, applications should call tcsetattr() then call tcgetattr() in order to determine what baud rates were actually selected.
The tcsetattr() function can be interrupted in the following situations:
See also the RATIONALE section in tcgetattr() .
Using an input baud rate of 0 to set the input rate equal to the output rate may not necessarily be supported in a future version of this volume of IEEE Std 1003.1-2001.
cfgetispeed() , tcgetattr() , the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 11, General Terminal Interface, <termios.h>, <unistd.h>