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Re: readf and structures [message #53482 is a reply to message #53481]

Tue, 10 April 2007 08:34

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Wox writes:

> Is there an easy way of printing arrays of structures to a file and
> read them in again, without reading the fields separate?
>
> This doesn't work (also tried with specifying formats):
>
> tout={a:0.,b:'name'}
> tin={a:0.,b:''}
>
> openw,lun,'c:\test.txt',/get_lun
> printf,lun,tout
> close,lun
> free_lun,lun
>
> openr,lun,'c:\test.txt',/get_lun
> readf,lun,tin
> close,lun
> free_lun,lun

This basically doesn't work because you have a string field.
All variables in IDL have a defined length, EXCEPT strings.
Thus, unless you can tell IDL how long your strings are,
it just keeps reading until it gets to the end of an input
line.

One way to tell IDL how long your strings are is to use
the XDR format for input/output. Thus, these commands would
work for you:

tout={a:0.,b:'name'}
tin={a:0.,b:''}

openw,lun,'test.txt',/get_lun, /xdr
writeu,lun,tout
free_lun,lun

openr,lun,'test.txt',/get_lun, /xdr
readu,lun,tin
free_lun,lun

Note that there is no need to have a CLOSE statement in your
code. FREE_LUN both closes the logical unit and frees it up
for future use.

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: readf and structures By: Benjamin Hornberger on Tue, 10 April 2007 09:40
		Re: readf and structures By: David Fanning on Tue, 10 April 2007 10:30
		Re: readf and structures By: Wox on Tue, 10 April 2007 08:38
		Re: readf and structures By: Benjamin Hornberger on Tue, 10 April 2007 07:52
		Re: readf and structures By: David Fanning on Tue, 10 April 2007 08:34

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