The simplest way to run a task is to enter its name on the input command line followed by a <CR>, as in,
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1.0cm > fdump
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The task will then prompt you for the value of all the required parameters. It will first display the current value of each parameter; if that value is OK then you can simple hit <CR> to accept it, otherwise enter the new value and hit <CR>. Note that you will not be prompted for any hidden parameters and the task will simply assume the default values (which can be listed with the plist command as shown above).
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If you know the value of any or all of the required task parameters, you may alternatively enter their value directly on the command line in the same order as listed by plist. The task will then only prompt you for the values of any remaining non-hidden parameters which were not entered on the command line. The file crabk.fits can be found in the testdata directory. For example,
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1.0cm > fdump crabk.fits STDOUT RATE 1-20
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will list the first 20 rows of the 'RATE' column in the FITS file crabk.fits onto the standard output device (STDOUT). As before, the task will assume the default value for any hidden parameters.
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You may override the default value of a hidden parameter in one of 3 ways: by specifying the new value on the command line, by using the pset command or by editing the par file. In the first method, the specification of the hidden parameters must follow any required parameters that are also given on the command line, as in,
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1.0cm > fdump crabk.fits STDOUT prhead=yes prdata=no
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This supplies values for the first 2 parameters, just like in the previous example, and then specifies that the 'prhead' parameter should have the value 'yes' and the 'prdata' parameter should have the value 'no'.
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The other way to specify the value of any parameter, including the hidden parameters, is through the pset command.
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1.0cm > pset fdump
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will prompt you in sequence for the value of every parameter in the fdump task. The value of an individual parameter may also be defined by specifying the name and value of the parameter on the command line.
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1.0cm > pset fdump skip=5
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This example sets the skip parameter in the fdump task equal to 5. Note that the pset command does not execute the task, but instead merely sets the default parameter values for the all subsequent runs of the task. To reset all parameters to their default value, use
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1.0cm > punlearn fdump
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