Write to a file. libc subroutines will use this system routine for output to all files, including stdout—so if you need to generate any output, for example to a serial port for debugging, you should make your minimal write capable of doing this. The following minimal implementation is an incomplete example; it relies on a outbyte subroutine (not shown; typically, you must write this in assembler from examples provided by your hardware manufacturer) to actually perform the output.
int write(int file, char *ptr, int len) {
int todo;
for (todo = 0; todo < len; todo++) {
outbyte (*ptr++);
}
return len;
}
tengyifei
commented
8 years ago
Write to a file. libc subroutines will use this system routine for output to all files, including stdout—so if you need to generate any output, for example to a serial port for debugging, you should make your minimal write capable of doing this. The following minimal implementation is an incomplete example; it relies on a outbyte subroutine (not shown; typically, you must write this in assembler from examples provided by your hardware manufacturer) to actually perform the output.