Reading BYTE Fields From An Informix Unload

Exporting records from an Informix table is simple using the UNLOAD TO command. This creates a delimited text file with a row for each record and the fields of the record delimited by the specified delimiter. Useful for data archive the files can easily be restored or processed with a Python script.

One complexity exists; if the record contains a BYTE (BLOB) field the contents are dumped hex encoded. This is not base64. To read these files take the hex encoded string value and decode it with the faux code-page hex: content.decode("hex")

The following script reads an Informix unload file delimited with pipes ("|") decoding the third field which was of the BYTE type.

rfile = open(ARCHIVE_FILE, 'r')
counter = 0
row = rfile.readline()
while row:
    counter += 1
    print(
        'row#{0} @ offset {1}, len={2}'
        .format(counter, rfile.tell(), len(row), )
    )
    blob_id, content, mimetype, filename, tmp_, tmp_ = row.split('|')
    content = content.decode("hex")
    print('  BLOBid#{0} "{1}" ({2}), len={3}'.format(
        blob_id, filename, mimetype, len(content)
    ))
    if mimetype == 'application/pdf':
        if '/' in filename:
            filename = filename.replace('/', '_')
        wfile = open('wds/{0}.{1}.pdf'.format(blob_id, filename, ), 'wb')
        wfile.write(content)
        wfile.close()