--- name: "termios.h" section: "0p" platform: "linux" package: "man-pages" version: "6.19-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/termios.h" --- # termios.h(0p) define values for termios ## PROLOG This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. ## NAME termios.h — define values for termios ## SYNOPSIS ``` #include ``` ## DESCRIPTION The *\* header shall contain the definitions used by the terminal I/O interfaces (see *Chapter 11*, *General Terminal Interface* for the structures and names defined). ### The termios Structure The *\* header shall define the following data types through **typedef**: - **cc\_t** Used for terminal special characters. - **speed\_t** Used for terminal baud rates. - **tcflag\_t** Used for terminal modes. The above types shall be all unsigned integer types. The implementation shall support one or more programming environments in which the widths of **cc\_t**, **speed\_t**, and **tcflag\_t** are no greater than the width of type **long**. The names of these programming environments can be obtained using the *confstr*() function or the *getconf* utility. The *\* header shall define the **termios** structure, which shall include at least the following members: ``` tcflag_t c_iflag Input modes. tcflag_t c_oflag Output modes. tcflag_t c_cflag Control modes. tcflag_t c_lflag Local modes. cc_t c_cc[NCCS] Control characters. ``` The *\* header shall define the following symbolic constant: - NCCS Size of the array *c\_cc* for control characters. The *\* header shall define the following symbolic constants for use as subscripts for the array *c\_cc*: | | | | | --- | --- | --- | | **Subscript Usage** | | **Canonical Mode** | **Non-Canonical Mode** | **Description** | | VEOF | | EOF character. | | VEOL | | EOL character. | | VERASE | | ERASE character. | | VINTR | VINTR | INTR character. | | VKILL | | KILL character. | | | VMIN | MIN value. | | VQUIT | VQUIT | QUIT character. | | VSTART | VSTART | START character. | | VSTOP | VSTOP | STOP character. | | VSUSP | VSUSP | SUSP character. | | | VTIME | TIME value. | The subscript values shall be suitable for use in **#if** preprocessing directives and shall be distinct, except that the VMIN and VTIME subscripts may have the same values as the VEOF and VEOL subscripts, respectively. ### Input Modes The *\* header shall define the following symbolic constants for use as flags in the *c\_iflag* field. The *c\_iflag* field describes the basic terminal input control. - BRKINT Signal interrupt on break. - ICRNL Map CR to NL on input. - IGNBRK Ignore break condition. - IGNCR Ignore CR. - IGNPAR Ignore characters with parity errors. - INLCR Map NL to CR on input. - INPCK Enable input parity check. - ISTRIP Strip character. - IXANY Enable any character to restart output. - IXOFF Enable start/stop input control. - IXON Enable start/stop output control. - PARMRK Mark parity errors. ### Output Modes The *\* header shall define the following symbolic constants for use as flags in the *c\_oflag* field. The *c\_oflag* field specifies the system treatment of output. - OPOST Post-process output. - ONLCR Map NL to CR-NL on output. - OCRNL Map CR to NL on output. - ONOCR No CR output at column 0. - ONLRET NL performs CR function. - OFDEL Fill is DEL. - OFILL Use fill characters for delay. - NLDLY Select newline delays: - NL0 Newline type 0. - NL1 Newline type 1. - CRDLY Select carriage-return delays: - CR0 Carriage-return delay type 0. - CR1 Carriage-return delay type 1. - CR2 Carriage-return delay type 2. - CR3 Carriage-return delay type 3. - TABDLY Select horizontal-tab delays: - TAB0 Horizontal-tab delay type 0. - TAB1 Horizontal-tab delay type 1. - TAB2 Horizontal-tab delay type 2. - TAB3 Expand tabs to spaces. - BSDLY Select backspace delays: - BS0 Backspace-delay type 0. - BS1 Backspace-delay type 1. - VTDLY Select vertical-tab delays: - VT0 Vertical-tab delay type 0. - VT1 Vertical-tab delay type 1. - FFDLY Select form-feed delays: - FF0 Form-feed delay type 0. - FF1 Form-feed delay type 1. ### Baud Rate Selection The *\* header shall define the following symbolic constants for use as values of objects of type **speed\_t**. The input and output baud rates are stored in the **termios** structure. These are the valid values for objects of type **speed\_t**. Not all baud rates need be supported by the underlying hardware. - B0 Hang up - B50 50 baud - B75 75 baud - B110 110 baud - B134 134\.5 baud - B150 150 baud - B200 200 baud - B300 300 baud - B600 600 baud - B1200 1200 baud - B1800 1800 baud - B2400 2400 baud - B4800 4800 baud - B9600 9600 baud - B19200 19200 baud - B38400 38400 baud ### Control Modes The *\* header shall define the following symbolic constants for use as flags in the *c\_cflag* field. The *c\_cflag* field describes the hardware control of the terminal; not all values specified are required to be supported by the underlying hardware. - CSIZE Character size: - CS5 5 bits - CS6 6 bits - CS7 7 bits - CS8 8 bits - CSTOPB Send two stop bits, else one. - CREAD Enable receiver. - PARENB Parity enable. - PARODD Odd parity, else even. - HUPCL Hang up on last close. - CLOCAL Ignore modem status lines. The implementation shall support the functionality associated with the symbols CS7, CS8, CSTOPB, PARODD, and PARENB. ### Local Modes The *\* header shall define the following symbolic constants for use as flags in the *c\_lflag* field. The *c\_lflag* field of the argument structure is used to control various terminal functions. - ECHO Enable echo. - ECHOE Echo erase character as error-correcting backspace. - ECHOK Echo KILL. - ECHONL Echo NL. - ICANON Canonical input (erase and kill processing). - IEXTEN Enable extended input character processing. - ISIG Enable signals. - NOFLSH Disable flush after interrupt or quit. - TOSTOP Send SIGTTOU for background output. ### Attribute Selection The *\* header shall define the following symbolic constants for use with *tcsetattr*(): - TCSANOW Change attributes immediately. - TCSADRAIN Change attributes when output has drained. - TCSAFLUSH Change attributes when output has drained; also flush pending input. ### Line Control The *\* header shall define the following symbolic constants for use with *tcflush*(): - TCIFLUSH Flush pending input. - TCIOFLUSH Flush both pending input and untransmitted output. - TCOFLUSH Flush untransmitted output. The *\* header shall define the following symbolic constants for use with *tcflow*(): - TCIOFF Transmit a STOP character, intended to suspend input data. - TCION Transmit a START character, intended to restart input data. - TCOOFF Suspend output. - TCOON Restart output. The *\* header shall define the **pid\_t** type as described in *\*. The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided. ``` speed_t cfgetispeed(const struct termios *); speed_t cfgetospeed(const struct termios *); int cfsetispeed(struct termios *, speed_t); int cfsetospeed(struct termios *, speed_t); int tcdrain(int); int tcflow(int, int); int tcflush(int, int); int tcgetattr(int, struct termios *); pid_t tcgetsid(int); int tcsendbreak(int, int); int tcsetattr(int, int, const struct termios *); ``` *The following sections are informative.* ## APPLICATION USAGE The following names are reserved for XSI-conformant systems to use as an extension to the above; therefore strictly conforming applications shall not use them: | | | | | --- | --- | --- | | CBAUD | EXTB | VDSUSP | | DEFECHO | FLUSHO | VLNEXT | | ECHOCTL | LOBLK | VREPRINT | | ECHOKE | PENDIN | VSTATUS | | ECHOPRT | SWTCH | VWERASE | | EXTA | VDISCARD | ## RATIONALE None. ## FUTURE DIRECTIONS None. ## SEE ALSO ***\*** The System Interfaces volume of POSIX.1‐2017, *cfgetispeed()*, *cfgetospeed()*, *cfsetispeed()*, *cfsetospeed()*, *confstr()*, *tcdrain()*, *tcflow()*, *tcflush()*, *tcgetattr()*, *tcgetsid()*, *tcsendbreak()*, *tcsetattr()* The Shell and Utilities volume of POSIX.1‐2017, *Chapter 11*, *General Terminal Interface*, *getconf* ## COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting\_bugs.html .