Re: writeu, printf, readu/f 2 file

[Martin Schultz <martin.schultz(at)dkrz.de>]

Craig Markwardt wrote:
> 
> Without delving into too much detail about your specific program, I
> can say that you should pay a lot more attention to your output
> formatting.  Don't assume, simply because you print it out one way, it
> can be read the same way.  For example:
> 
> IDL> openw, 50, 'test.dat'
> IDL> printf, 50, 1, '2 3', 4
> IDL> close, 50
> IDL> openr, 50, 'test.dat'
> IDL> a = 0 & b = '' & c = 0
> IDL> readf, 50, a, b, c
> % READF: End of file encountered. Unit: 50
>          File: test.dat
> % Execution halted at:  $MAIN$
> 
> Hmmm, why did this fail?  Well, the string B is very greedy and it
> consumes everything to the end of the line, including the "4".
> 
> Mixing formatted and unformatted data in a file can be tricky.  The
> problem is that when you read formatted data the file pointer can
> advance unpredictably.  Better to read and write the data
> intermediately to a string buffer.
> 
> Craig
> 

... or use a byte array to represent strings in a binary file. I have
a little utility program available that will convert strings (or
string arrays) to byte arrays. To go back, you can simply use
String(thearray). The program is here:

http://www.mpimet.mpg.de/~schultz.martin/idl/html/src/martin_schultz/str2byte.pro

Cheers,
Martin

-- 
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[[ Dr. Martin Schultz   Max-Planck-Institut fuer Meteorologie    [[
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