The s6-fdholder-store program
s6-fdholder-store connects to a fd-holding daemon listening on a Unix domain socket, and gives it a copy of one of its open file descriptors for the daemon to hold.
Interface
s6-fdholder-store [ -d fd ] [ -T fdtimeout ] [ -t timeout ] path id
- s6-fdholder-store connects to a s6-fdholderd server process listening on path.
- It attempts to pass a copy of its standard input, or of its descriptor fd, to the server, with identifier id.
Options
- -d fd : store descriptor number fd. By default, fd is 0 (i.e. the program's stdin will be stored).
- -T fdtimeout : the descriptor is stored with an expiration time of fdtimeout milliseconds, which means the s6-fdholderd daemon will close and get rid of the descriptor after this time. By default, fdtimeout is 0, which means infinite - no expiration time.
- -t timeout : if the operation cannot be processed in timeout milliseconds, then fail with an error message. Communications with the server should be near-instant, so this option is only here to protect users against programming errors (connecting to the wrong socket, for instance).
Exit codes
- 0: success.
- 1: the server denied the operation. The meaning of the error messages is explained here.
- 100: wrong usage.
- 111: system call failed - this includes attempting to connect to a nonexistent socket, or one where no s6-fdholderd daemon is listening.
Usage example
s6-ipcserver-socketbinder /tmp/mysocket s6-fdholder-store /service/fdholderd/s MYSOCKET
will open a Unix domain socket, bind it to /tmp/mysocket and listen to incoming connections, then give it to a s6-fdholderd instance listening on /service/fdholderd/s, with no expiration date, with the "MYSOCKET" identifier. Another program will be able to retrieve the socket later, using s6-fdholder-retrieve.