Beaglebone Analog Input read() results in 4 bytes

After writing some C code to read the analog inputs, it became clear that reading analog inputs via the file system (.../ain1, etc.), the system returns 4 bytes for each read. The bytes are the ASCII characters for the digits 0-9 (values got from 0-4095), and if the reading is less than 4 digits, the byte = \x00 is placed in trailing locations. The \x00 byte is the string terminator for C, and is not present for readings that are 4 digits long. This could explain why channels shift when reading the analog values via Tcl reads: the area the 4-byte value is read into might not have a string terminator.

So, the technique is to read into a buffer of 5 or more bytes, then make sure the 5th byte is a \x00 by either setting the whole area to \x00 first or storing \x00 there after the read, then the C string will be properly terminated.