The sas7bdat file format is not documented...and it varies slightly across releases as the format is enhanced. Only SAS software can read the content and all of its attributes reliably.
However, you can (on Windows) use the SAS local data provider via OLE DB to read SAS data sets without having full SAS installed. I have a PowerShell example here -- the same could be invoked within a C program. You can download the SAS local OLE DB provider from SAS support (link in the blog).
If you have access to a SAS server and want to read SAS data from your SAS environment using other applications, look at the saspy Python library.
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