VILLASnode/documentation/clients/File.md

File

The file node-type can be used to log or replay sample values to disk.

Configuration

Every file node supports the following settings:

in

Specifies the path to a file which contains data for replaying. See below for a description of the file format.

out

Specifies the path to a file where samples will be written to. This setting allows to add special paceholders for time and date values. See strftime(3) for a list of supported placeholder.

Example:

out = "logs/measurements_%Y-%m-%d_%H-%M-%S.log"

will create a file called: path_of_working_directory/logs/measurements_2015-08-09_22-20-50.log

file_mode

Specifies the mode which should be used to open the output file. See open(2) for an explanation of allowed values. The default value is w+ which will start writing at the beginning of the file and create it in case it does not exist yet.

epoch_mode

This setting allows to select the behaviour of the following epoch setting. It can be used to adjust the point in time when the first value should be read.

The behaviour of epoch is depending on the value of epoch_mode.

• epoch_mode = now: The first value is read at now + epoch seconds.
• epoch_mode = relative: The first value is read at start + epoch seconds.
• epoch_mode = absolute: The first value is read at epoch seconds after 1970-01-01 00:00:00.

rate

By default rate has the value 0. If the value is non-zero,

Example

@todo Add extract of example.conf

File Format

This node-type uses a simple human-readable format to save samples: The format is similiar to a conventional CSV (comma seperated values) file. Every line in a file correspondents to a message / sample of simulation data. The columns of a line are seperated by whitespaces (tabs or spaces). The columns are defined as follows:

1. Seconds in floating point format since 1970-01-01 00:00:00 (aka Unix epoch timestamp: date +%s).
2. Sequence number
3. Up to MSG_VALUES floating point values per sample. The values are seperated by whitespaces as well.

Example

This example shows a dump with three values per sample:

1438959964.162102394	6	3.489760	-1.882725	0.860070
1438959964.261677582	7	2.375948	-2.204084	0.907518
1438959964.361622787	8	3.620115	-1.359236	-0.622333
1438959964.461907066	9	5.844254	-0.966527	-0.628751
1438959964.561499526	10	6.317059	-1.716363	0.351925
1438959964.661578339	11	6.471288	-0.159862	0.123948
1438959964.761956859	12	7.365932	-1.488268	-0.780568