6. Client Commands¶

Each section below documents one of the commands available in the Compound Pi command line client. Many commands accept an address or list of addresses. Addresses must be specified in dotted-decimal format (no hostnames). Inclusive ranges of addresses are specified by two dash-separated addresses. Lists of addresses, or ranges of addresses are specified by comma-separating each list item.

The following table demonstrates various examples of this syntax:

Syntax	Expands To
`192.168.0.1`	192.168.0.1
`192.168.0.1-192.168.0.5`	192.168.0.1 192.168.0.2 192.168.0.3 192.168.0.4 192.168.0.5
`192.168.0.1,192.168.0.3`	192.168.0.1 192.168.0.3
`192.168.0.1,192.168.0.3-192.168.0.5`	192.168.0.1 192.168.0.3 192.168.0.4 192.168.0.5
`192.168.0.1-192.168.0.3,192.168.0.5`	192.168.0.1 192.168.0.2 192.168.0.3 192.168.0.5

It is also worth noting that if readline is installed (which it is on almost any modern Unix platform), the command line supports Tab-completion for commands and most parameters, including defined server addresses.

6.1. add¶

Syntax: add addresses

The add command is used to manually define the set of Pi’s to communicate with. Addresses can be specified individually, as a dash-separated range, or a comma-separated list of ranges and addresses.

6.2. capture¶

Syntax: capture [addresses]

The capture command causes the servers to capture an image. Note that this does not cause the captured images to be sent to the client. See the download command for more information.

If no addresses are specified, a broadcast message to all defined servers will be used in which case the timestamp of the captured images are likely to be extremely close together. If addresses are specified, unicast messages will be sent to each server in turn. While this is still reasonably quick there will be a measurable difference between the timestamps of the last and first captures.

6.3. clear¶

Syntax: clear [addresses]

The clear command can be used to clear the in-memory image store on the specified Pi servers (or all Pi servers if no address is given. The download command automatically clears the image store after successful transfers so this command is only useful in the case that the operator wants to discard images without first downloading them.

6.4. config¶

Syntax: config

The config command is used to display the current client configuration. Use the related “set” command to alter the configuration.

6.5. download¶

Syntax: download [addresses]

The download command causes each server to send its captured images to the client. Servers are contacted consecutively to avoid saturating the network bandwidth. Once images are successfully downloaded from a server, they are wiped from the server.

6.6. exit¶

Syntax: exit|quit

The exit command is used to terminate the application. You can also use the standard UNIX Ctrl+D end of file sequence to quit.

6.7. find¶

Syntax: find [count]

The find command is typically the first command used in a client session to locate all Pi’s on the current subnet. If a count is specified, the command will display an error if the expected number of Pi’s is not located.

See also: add, remove, servers, identify.

cpi> find
cpi> find 20

6.8. framerate¶

Syntax: framerate rate [addresses]

The framerate command is used to set the capture framerate of the camera on all or some of the defined servers. The rate can be specified as an integer or floating-point number, or as a fractional value. The framerate of the camera influences the capture mode that the camera uses. See the camera hardware chapter of the picamera documentation for more information.

If no address is specified then all currently defined servers will be targetted. Multiple addresses can be specified with dash-separated ranges, comma-separated lists, or any combination of the two.

6.9. help¶

Syntax: help [command]

The ‘help’ command is used to display the help text for a command or, if no command is specified, it presents a list of all available commands along with a brief description of each.

6.10. identify¶

Syntax: identify [addresses]

The identify command can be used to locate a specific Pi server (or servers) by their address. It sends a command causing the camera’s LED to blink on and off for 5 seconds. If no addresses are specified, the command will be sent to all defined servers (this can be useful after the find command to determine whether any Pi’s failed to respond due to network issues).

6.11. quit¶

Syntax: exit|quit

The exit command is used to terminate the application. You can also use the standard UNIX Ctrl+D end of file sequence to quit.

6.12. remove¶

Syntax: remove addresses

The remove command is used to remove addresses from the set of Pi’s to communicate with. Addresses can be specified individually, as a dash-separated range, or a comma-separated list of ranges and addresses.

6.13. resolution¶

Syntax: resolution width x height [addresses]

The resolution command is used to set the capture resolution of the camera on all or some of the defined servers. The resolution of the camera influences the capture mode that the camera uses. See the camera hardware chapter of the picamera documentation for more information.

If no address is specified then all currently defined servers will be targetted. Multiple addresses can be specified with dash-separated ranges, comma-separated lists, or any combination of the two.

6.14. servers¶

Syntax: servers

The servers command is used to list the set of servers that the client expects to communicate with. The content of the list can be manipulated with the find, add, and remove commands.

6.15. set¶

Syntax: set name value

The set command is used to alter the value of a client configuration variable. Use the related config command to view the current configuration.

6.16. status¶

Syntax: status [addresses]

The status command is used to retrieve configuration information from servers. If no addresses are specified, then all defined servers will be queried.