:sig
String file_read(u64 h, u64 len)

:params
h : handle from file_open() opened for reading
len : maximum number of bytes to read
return value : up to `len` bytes from the current offset (shorter at end of file)

:content
Reads up to `len` bytes starting at the handle's current offset and advances the offset. Returns fewer bytes (or `""`) at end of file. Use `file_seek()` to move the offset, or `file_pread()` to read at an absolute offset without moving it.

:example
u64 w = file_open("/tmp/doc-read.txt", "w");
file_write(w, "hello world");
file_close(w);
u64 r = file_open("/tmp/doc-read.txt", "r");
print(file_read(r, 5), "\n");
file_close(r);

:see
>sys
file_open
file_pread
file_seek
file_close