Formatting fread binary file (converting from FORTRAN script)

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Darcy Cordell 2020-7-15

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评论： dpb 2020-7-16

I am converting some Fortran to MATLAB and am stuck early on when trying to load a binary file. I know MATLAB well but I have not had much experience loading binary files. I have mostly had to only load text files in the past. Furthermore, I am a newbie to Fortran and the I/O commands and generally lower-level language is a challenge.

The Fortran script has a read statement:

READ(Ifile,FMT='(A70)',ERR=993) Tag

My understanding is that this command has a file id (Ifile) similar to "fid" which has been called using a previous OPEN command (similar to fopen).

Furthermore, the '(A70)' specifies that the read command should read 70 bytes of the file as a character (A).

The result is stored in the variable "Tag".

However, in MATLAB, if I use

Tag = fread(fid,70,'char')

I don't get the same result as Fortran.

What am I missing here? Any help is appreciated.

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James Tursa 2020-7-16

编辑：James Tursa 2020-7-16

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You might have to skip 4 bytes first, and use '*char' formatting (with the asterisk) to get a char result. E.g., you might have to use some variation of these lines:

fread(fid,[1 4],'*uint8');
Tag = fread(fid,[1 70],'*char',4);

dpb 2020-7-16

Specifically, the file could be SEQUENTIAL or DIRECT. If it is direct access, then there will be as James notes a record marker at beginning (and perhaps end) of each record that will have to skip; a sequential file will have only record terminators and can be variable length; direct access is fixed-length.

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