A file pointer to the open destination file for the characters.
The buffer that is the source of the characters.
The number of characters to write.
This function reads a given number of characters from a buffer and writes them to an open file.
The following example writes the characters 'e', 'f', and 'g' to a file.
Gamma> fw = open("mywritencharsfile.dat", "w");
#<File:"mywritencharsfile.dat">
Gamma> buf = buffer (101, 102, 103, 104);
#{efgh}
Gamma> write_n_chars (fw, buf, 3);
3
Gamma>