tcgetattr(3C)

NAME

tcgetattr, tcsetattr − Get or set terminal attributes.

SYNOPSIS

#include <termios.h>

int tcgetattr (fildes, termios_p)
int fildes;
struct termios ∗termios_p;

int tcsetattr (fildes, optional_actions, termios_p)
int fildes;
int optional_actions;
struct termios ∗termios_p;

DESCRIPTION

The tcgetattr() and tcsetattr() functions are defined in the POSIX 1003.1 standard and used in the OCS and BCS standards. CX/UX applications which are not POSIX/OCS/BCS compliant can use these functions.

tcgetattr gets the attributes associated with the terminal device referenced by fildes. These attributes are returned to the user via the termios structure pointed to by termios_p. A background process may call this function, but the attributes may be changed by a subsequent foreground process call to tcsetattr.

Tcsetattr sets the attributes associated with the terminal device referenced by fildes. These attributes are passed into the system via the user modified termios structure pointed to by termios_p. The methods of performing this action are described by one of the optional_actions as follows:

TCSANOW
The change shall occur immediately.

TCSADRAIN
The change shall occur after all output written to fildes has been transmitted (drained). This option should be used when changing parameters that affect output (e.g., Preventing output from disappearing at low baud rates).

TCSAFLUSH
The change shall occur after 1) all output written to fildes has been transmitted (drained), and 2) all input that has been received but not read has been discarded (flushed).

The optional_actions constants are defined in <termios.h>. Background processes may not call tcsetattr. Attempts to do so will result in a SIGTTOU signal being sent to the calling process and all members of its process group. The SIGTTOU signal will stop the calling process and all members of its process group unless the calling process is blocking or ignoring this signal.

NOTES

CX/UX does not support separate line rates for terminal devices. As a result, all references to input rates actually refer to output rates. Therefore, the input rate should be specified by the same value as the output rate when using tcsetattr. It is best to use cfsetispeed(3C) with its argument speed set to B0 allowing the input rate to be automatically specified by the value of the output baud rate. This assumes that cfsetospeed(3C) has been previously called. If both input and output baud rates do not match, the tcsetattr function call will fail with errno set to [EINVAL].

DIAGNOSTICS

Upon successful completion, a value of zero is returned by both functions. If not, a value of -1 is returned and errno is set.

Errno is set to one of the following values for tcgetattr:

[EBADF]
Fildes is not a valid open file descriptor.

[ENOTTY] Fildes is not associated with a terminal device.

Errno is set to one of the following values for tcsetattr:

[EBADF]
Fildes is not a valid open file descriptor.

[EINVAL] The optional_actions argument is not a proper value as defined in <termios.h>, or an attempt was made to change an attribute represented in the termios structure to an unsupported value (e.g., input baud rate not equivalent to output baud rate).

[ENOTTY] Fildes is not associated with a terminal device.

CX/UX Programmer’s Reference Manual

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