I keep having to look this up, so I’m going to put it here for easy reference:

### Open a File

 h = outfile("new_file.txt", "w") h = infile("existing_file.txt") h = outfile("partial_file.txt", "a") 
Opens new file for writing, existing file for reading, and partial file for appending, respectively.

### Write to a file

 write("Hello World!\n", h) fprintf(h, "gm = %f", OP("/M23" "gm")) print(OP("/M23" "gm"), h) pprint(OP("/M23" "gm"), h) 

Write “Hello World!” to a file (newlines are explicit); construct formatted string and write to file; print using native format to a file; pretty-print (useful for nested lists etc) to a file. File handle is h.

### Read from a file

 str = lineread(h) 

Reads a single line as a string