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17.4.5 Output Modes

This section describes the terminal flags and fields that control how output characters are translated and padded for display. All of these are contained in the c_oflag member of the struct termios structure.

The c_oflag member itself is an integer, and you change the flags and fields using the operators &, |, and ^. Don't try to specify the entire value for c_oflag—instead, change only specific flags and leave the rest untouched (see Setting Modes).

— Macro: tcflag_t OPOST

If this bit is set, output data is processed in some unspecified way so that it is displayed appropriately on the terminal device. This typically includes mapping newline characters ('\n') onto carriage return and linefeed pairs.

If this bit isn't set, the characters are transmitted as-is.

The following three bits are effective only if OPOST is set.

— Macro: tcflag_t ONLCR

If this bit is set, convert the newline character on output into a pair of characters, carriage return followed by linefeed.

— Macro: tcflag_t OXTABS

If this bit is set, convert tab characters on output into the appropriate number of spaces to emulate a tab stop every eight columns. This bit exists only on BSD systems and GNU/Hurd systems; on GNU/Linux systems it is available as XTABS.

— Macro: tcflag_t ONOEOT

If this bit is set, discard C-d characters (code 004) on output. These characters cause many dial-up terminals to disconnect. This bit exists only on BSD systems and GNU/Hurd systems.