:sig
void file_append(String file_name, ...val)

:params
file_name : file to append to, created if missing
...val : one or more values appended in order
return value : none

:content
Appends one or more values to a file, creating it if needed. Each call takes an exclusive lock for the append, so concurrent appends are serialized and readers wait for them; you never manage locks yourself.

:example
file_unlink("/tmp/doc-append.txt");
file_append("/tmp/doc-append.txt", "a", "b", "c");
print(file_get_contents("/tmp/doc-append.txt"), "\n");

:see
>sys
file_put_contents
file_get_contents