open/append

[variable] open/rdonly

[variable] open/wronly

[variable] open/rdwr

[variable] open/read

[variable] open/write

[variable] open/creat

[variable] open/append

[variable] open/excl

[variable] open/noctty

[variable] open/nonblock

[variable] open/trunc

[variable] open/sync

Chicken flags to use for file-open.