CL Tips & Tricks

To redirect the output of a command to a file, you can use either an explicit filename or a temporary one in a script by doing something like:

string dummy
dummy = mktemp ("cen")

imcent (image, dummy, ...., >> dummy)


When writing a script you may sometimes want to set parameters for some tasks, but not have those parameters persist in your uparm directory once the task is completed (e.g. when setting pset parameters that are only needed for the particular script). As long as you set all other needed parameters and accept defaults for unspecified parameters, simply reset the value of your uparm directory within the script so a temporary uparm file is created. For example,

set uparm = "tmp$"
rimexam.banner = no
imexam (......)
delete ("tmp$*.par", ver-)


The rimexam parameter file will be updated to one created in /tmp, but once the script exits your environment still uses the old uparm directory which has the original parameters (that's why you use 'set' and not 'reset').

Although IRAF lacks an equivalent to sprintf, you can get similar behavior by scanning the output of the printf statement. For example, to define image names using zero-filled fields you could use:

cl> printf("lris%04d.fits\n", i) | scan( s1)

where i is set to an integer value, and s1 contains the resulting image name (i=1 gives s1="lris0001.fits", etc.) Note that the newline character "\n" in the format statement is required to complete the scan operation.

Note that if the formatted string is to contain embedded spaces, you'll need to scan the output of the printf into a variable of type "struct", such as the builtin variable "line". For example:

    cl> printf("Data section is [%d:%d,%d:%d]\n",
    	x1, x2, y1, y2) | scan( line)
    cl> hedit( image, "DATASEC", line, add+)

You can use the translit task as a stream editor to help in parsing comma-delimited strings. For example, to parse this header card:

cc> imhead lris0106 l+ | match WINDOW
WINDOW = '1,0,0,2048,2048' /


You can use this set of commands in your script:

hselect (image, "window", "yes") | \
translit ("STDIN", ",", " ") | \
scan (winchip, winxstart, winystart, winxlen, winylen)


There are 9 variables for your use pre-defined in the cl: x,y,z for reals, i,j,k for integers, and s1,s2,s3 for strings. These can be used for calculating parameter values, or for generating file names, for example.

cl> x = 3
cl> y = x**2
cl> print (y)
9.

cl> i = 1
cl> s1 = "file" + i
cl> print (s1)
file1
cl> i = i + 1
cl> print ("file"+i)
file2


Output from a command may be read into a local script variable directly using the scan() function. For example,

cl> hselect("dev$pix","otime",yes) | scan(x)

For more information on commands that are built into the CL, see help language.

The scanf and printf functions, which work similarly to the equivalent C functions, can be used to read or write formatted input. For example,


cl> printf("pi = %g\n", 3.14159)
pi = 3.14159
or

cl> s1 = "12:34:56.7"
cl> print(s1) | scanf("%d:%d:%g",hr,min,sec)


It is possible to edit the value of a parameter in the epar menu. Move to the line on which the parameter is shown as if you are going to re-type its value. Then type Ctrl-U, Ctrl-L to enter the edit mode (for vi users, emacs users should type ESC-Ctrl-K). Use the left/right arrow keys to move within the parameter string and delete to erase unwanted characters. Type the new characters and then RETURN to complete the editing process.

In V2.10.4p2 and later the "d_trace" command will print a detailed execution of a CL script allowing you to more easily find where a script crashes. This command is a toggle, typing it again returns you to normal operation.

In epar a pset parameter can be edited from the current session using the :e command.

By editing a task mode parameter and setting it to 'm', the task will execute in menu mode meaning that whenever it is executed the task will first go into epar automatically and can be run using :go or by exiting.

It's possible to change a task parameter min/max value by setting the parameter p_minimum or p_maximum attribute. For example,

rv> fxcor.minwidth.p_min=1

It is possible to change a task parameter mode from "hidden" to "auto" so that you are asked for a value each time. Or, you can change a parameter to stop asking you for values. For example,

cl> display.z1.p_mode = "a"
cl> display.frame.p_mode = "h"

In IRAF sexigesimal numbers are recognized as numbers and not strings so a real value keyword is created and the input number is converted to decimal. To add or modify the keyword so it is entered in the image header as a string value, use a dummy value to first force a string type keyword to be created and then change the value. For example,


cl> hedit pix newtime dummy add+ verify- show- upate+
cl> hedit pix newtime "1:20:30" verify- show- update+