PSRCHIVE user documentation: vap

1.0 Purpose

The Viewer of Archive Parameters, vap, is designed to interrogate headers and glean simple numerical quantities from the data contained inside pulsar archives. It is a terminal-based program that can be combined with the standard utilities awk and grep to produce large summary listings of multiple archives for the purpose of organisation, sorting and classification. It does not do any graphical visualisation or file manipulation.

2.0 Usage

vap is very simple to use, all commands are of the form 
vap options filenames
where the options can be anything from a large list of available parameters. For a full list of options, use: 
vap -h
Multiple filenames can be specified on the command line either individually or using wildcard characters.

3.0 Algorithms

vap serves primarily as a simple interface between the user and member functions of various classes in the PSRCHIVE scheme. It does not (in general) implement any additional algorithms.

4.0 Testing and examples

The header parameters in an archive are designed to provide information about the way the main body of data was observed, recorded and stored. This includes storage of characteristics like radio frequency, track duration, calibration status, number of frequency channels, etc. Many parameters are essential and will always be present in any archive header; these are listed first in the help text. Certain optional parameters are only available through the use of Archive or Integration Extension classes, these parameters are not stored in all archives and are included in a separate section of the help text. To access any of these basic storage parameters, a space-separated list should be passed (in parentheses) to vap using the "-c" argument. For example: 
vap -c "NAME RAJ DECJ INST PCAL FCAL" *.ar
The above command prints a formatted list containing the source name, sky coordinates, instrument used and calibration status of all archives with the ".ar" extension. It is possible to alter the formatting of the output using additional options described in the later section of the help text. One of the most useful is the "-n" option, which removes the column headings to make it easier to manipulate the output with awk, say. In addition, vap can display simple analytical information (like signal-to-noise ratio), using one or more of the extended options listed at the end of the help text. For example: 
vap -r *.ar
It is possible (in some cases) to combine these extended options with header parameters accessed through the "-c" argument. For example, S/N can be printed alongside observation length using the command: 
vap -rc *.ar

5.0 Known bugs and features that require implementation

  • None at this time.