In particular, the kind of commands you're looking for are:
w/infile (open a file for input, execute some code, and then close it)
w/outfile (same as w/infile but for output)
readc/readb (read a character/byte from an open file)
writec/writeb (write a character/byte to an open file)
Other useful operators are readfile, writefile, drain and w/stdout. Note that most of the Arc functions related to file manipulation assume that the file you're editing is Arc code (e.g. readfile) so watch out for that. I haven't yet found an easy way to read the contents of a file into a string, but the following function works:
