os.create creates or truncates a file and returns a file object. Use write_string or write (for bytes), then close when done.
fmt := import("fmt")
os := import("os")f := os.create("/tmp/tengo_write.txt")
f.write_string("line 1\n")
f.write_string("line 2\n")
f.write(bytes("line 3\n"))
f.close()
fmt.println(string(os.read_file("/tmp/tengo_write.txt")))flags := os.o_wronly | os.o_append
f2 := os.open_file("/tmp/tengo_write.txt", flags, 0644)
f2.write_string("line 4\n")
f2.close()
fmt.println(string(os.read_file("/tmp/tengo_write.txt")))os.remove("/tmp/tengo_write.txt")try it
line 1 line 2 line 3 line 1 line 2 line 3 line 4