Note that the standard way to specify a path through the IRAF package hierarchy to a task in a particular subpackage is to separate the package names with periods (e.g., stsdas.hst_calib.foc.focgeom.newgeom).
st> imhead myfile.hhh
IRAF does not require you to type the complete command name-only enough of it to make it unique. For example, dir is sufficient for directory.
st> task1 filename | task2For example, if a particular task prints a large volume of textual output to the screen, you will often want to pipe it to page, which allows you to read the output one page at a time:
st> task1 filename | pageYou can also redirect output from any task or command to a file by using the greater-than symbol (>) as follows:
st> command > outputfile
st> taskname &
fi> help mkmultispec
The two most useful commands for handling parameters are:
Figure A.5: Displaying Parameter Settings with lpar
Setting parameters with eparam
The epar command is an interactive parameter set editor. It displays all of the parameters and their current settings on the screen. You can move around the screen using the arrow keys (also called cursor keys) and type new settings for any parameters you wish to change. Figure A.6 shows a sample of the epar editor at work (invoked by typing epar strfits).
Figure A.6: Editing -Parameters with epar
Parameter Data Types-What to Specify
Parameters are either required or hidden, and each parameter expects information of a certain type. Usually, the first parameter is required, and very often it expects a file name. Parameters are described in the online help for each task [include reference to help]. Hidden parameters, shown in parentheses in the online help and the lpar and epar listings, need not be specified at each execution because their default values frequently suffice.
Wise IRAF users will check the values of hidden parameters, as they often govern
important aspects of a task's behavior.
If you specify the wrong type of information for a parameter, epar will usually display an error message saying something like "Parameter Value is Out of Range." The message is displayed when you move to another parameter or if you press . Table A.1 lists the different parameter types.
Parameter Data Types
Full name of the file. Wild card characters (* and ?) are often allowed. Some tasks allow you to use special features when specifying file names, including "@" lists, IRAF networking syntax, and image section or group syntax. (See "File Management" below).
Whole number. Often the task will specify minimum or maximum values (see the help pages).
Floating point numbers, can be expressed in exponential notation. Often will have minimum and maximum values.
Logical "yes" or "no" values.
Any characters. Sometimes file names are specified as string.
Restoring Parameter Default Values
Occasionally, IRAF (or you) will get confused by your parameter values. To alleviate this confusion, you can restore the default parameters with the unlearn command. You can use unlearn on either a task or on an entire package.
The unlearn command generally will restore the parameters to reasonable values,
a big help if you are no longer sure which parameter values you have changed in a
A.2.5 Setting Environment Variables
IRAF uses environment variables to define which devices are used for certain operations. For example, your terminal type, default printer, and the disk and directory used for storing images are all defined through environment variables. Environment variables are set using the set command and are displayed using the show command. Table A.2 lists some of the environment variables that you might want to customize.
Example of Setting
Default printer for text
set printer = lp2
set term = xterm
Default printer for all graphics output
set stdplot = ps2
Default terminal display setting for image output (most users will want this set to either imt512 or imt800)
set stdimage = imt800
Default graphics device
set stdgraph = xterm
Allow or prevent overwriting of files
set clobber = yes
Default image type for output images. "imh" is original IRAF format, "hhh" is STSDAS GEIS format.
set imtype = "hhh"
If you are working with GEIS files, you should set imtype to "hhh". If you are
working with STIS and NICMOS data in FITS files, you can set imtype to
You can set your environment variables automatically each time you login to IRAF by adding the appropriate commands to your login.cl file. Use your favorite text editor to specify each variable on its own line. The show command with no arguments prints the names and current values of all environment variables.
A.2.6 File Management
This section describes:
When working with IRAF or STSDAS images, you need only specify the header file name-the tasks will automatically use the binary data file when -necessary.
When using wildcards with image-processing tasks, be sure to exclude the binary pixel files by ending your file name specification with an "h", for example: y*.??h
2 The binary data file format is host-dependent and may require translation before it can be moved to a computer using a different architecture.
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