NAME

tcdrain - wait for transmission of output

SYNOPSIS

#include <termios.h>

int tcdrain(int fildes);

DESCRIPTION

The tcdrain() function waits until all output written to the object referred to by fildes is transmitted. The fildes argument is an open file descriptor associated with a terminal.

Any attempts to use tcdrain() from a process which is a member of a background process group on a fildes associated with its controlling terminal, will cause the process group to be sent a SIGTTOU signal. If the calling process is blocking or ignoring SIGTTOU signals, the process is allowed to perform the operation, and no signal is sent.

RETURN VALUE

Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

ERRORS

The tcdrain() function will fail if:

[EBADF]

The fildes argument is not a valid file descriptor.

[EINTR]

A signal interrupted tcdrain().

[ENOTTY]

The file associated with fildes is not a terminal.

The tcdrain() function may fail if:

[EIO]

The process group of the writing process is orphaned, and the writing process is not ignoring or blocking SIGTTOU.

EXAMPLES

None.

APPLICATION USAGE

None.

FUTURE DIRECTIONS

In the ISO POSIX-1 standard, the possibility of an [EIO] error occurring is described in XBD specification, Terminal Access Control, but it is not mentioned in the tcdrain() interface definition. It has become clear that this omission was unintended, so it is likely that the [EIO] error will be reclassified as a "will fail" in a future issue of the POSIX standard.

SEE ALSO

tcflush(), <termios.h>, <unistd.h>, the XBD specification, General Terminal Interface.