Debugging with GDB: Console I/O

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E.13.6 Console I/O

By default and if not explicitly closed by the target system, the file descriptors 0, 1 and 2 are connected to the GDB console. Output on the GDB console is handled as any other file output operation (write(1, …) or write(2, …)). Console input is handled by GDB so that after the target read request from file descriptor 0 all following typing is buffered until either one of the following conditions is met:

• The user types Ctrl-c. The behaviour is as explained above, and the read system call is treated as finished.
• The user presses RET. This is treated as end of input with a trailing newline.
• The user types Ctrl-d. This is treated as end of input. No trailing character (neither newline nor ‘Ctrl-D’) is appended to the input.

If the user has typed more characters than fit in the buffer given to the read call, the trailing characters are buffered in GDB until either another read(0, …) is requested by the target, or debugging is stopped at the user’s request.