Thanks, I'll pass this on...(back)? (busybodiesRus?)
Chet Ramey wrote:
The original poster's speculation is correct. Bash is not allowed to read more input from stdin than it actually consumes, so commands that it runs get the intended input. To that end, it tries to detect whether or not the fd it is using for standard input is seekable: if it is, bash assumes that it can correctly position the file pointer by seeking backwards; if it is not, bash reads a character at a time. Bash uses lseek to the current file position to check this. If the lseek returns -1/EPIPE, bash assumes the fd is not seekable. If it returns 0, bash assumes that it can move around freely. Since bash is trying to seek backwards in the file, stdin is either a regular file or a tty (in which case bash assumes that reads are newline-delimited by the device driver). I suspect what happens is that isatty() returns 1 for serial devices, but reads are not newline-delimited. Chet
