IRAF and the CL

Working with Files

This section describes:

File Structures

Images used by IRAF and STSDAS consist of two files. The two files are always used together as a pair and will always have a file name that differs only in the last character of the extension:

STSDAS always expects both component files of a Generic Edited Information Set (GEIS) image to be kept together in the same directory. Both components must have the same root name.

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.

IRAF and STSDAS image formats are not similar in any way, other than that they each have two component files. The IRAF header is binary and has no fixed format, whereas the STSDAS format specifies 80 byte records consisting of ASCII text. The IRAF binary file consists of a grid of binary data preceded by a 512-byte binary description. The STSDAS binary file consists of a series of groups of binary data, each representing an entire image, and blocks of group description information called the Group Parameter Block (GPB).

See Chapter 3 on page 37 for more information about data formats.

Directory Specification

As we mentioned above, the two components of an STSDAS image are expected to be in the same directory, and tasks will look for these files in whatever directory you are currently located.*2

To navigate through directories, you should use the following commands:

Specifying Files

Most tasks in IRAF and STSDAS operate on files and expect you to specify a file name for one or more parameters. There are several types of special syntax that can be used with certain tasks when specifying file names. These syntax features include:

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

Using @-Files

File Structures
Directory Specification
Specifying Files

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