tcdrain - wait for transmission of output
#include <termios.h> int tcdrain(int fildes);
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.
Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.
The tcdrain() function will fail if:
- The fildes argument is not a valid file descriptor.
- A signal interrupted tcdrain().
- The file associated with fildes is not a terminal.
The tcdrain() function may fail if:
- The process group of the writing process is orphaned, and the writing process is not ignoring or blocking SIGTTOU.
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.
tcflush(), <termios.h>, <unistd.h>, the XBD specification, General Terminal Interface .
Derived from the POSIX.1-1988 standard.