Skipping bytes in binary file
12 views (last 30 days)
Show older comments
I have a binary file with the following values. The first 4 are each 2 bytes and double precision. The following are pairs of values of double precision. The bytes are unknown for the pair that follows. How can I use fread to skip the first 4 values (8 bytes) and extract the pairs?
1
2
3
4
1 2 4
2 2 5
4 4 4
2 Comments
Jan
on 29 Dec 2022
"The first 4 are each 2 bytes and double precision." - Double precision means 8 bytes per value.
"The following are pairs of values of double precision." - Which pairs? I see triples.
Accepted Answer
Voss
on 29 Dec 2022
You can just fread the appropriate number of bytes (i.e., the amount you want to skip). For example:
% read 4 double-precision numbers (32 bytes), and don't store the result
fread(fid,4,'double');
Or you can use fseek to move the file position indicator forward by the appropriate amount:
% move 32 bytes forward, effectively skipping those bytes
fseek(fid,32,'cof')
The next fread call reads from where fseek placed the file position indicator.
2 Comments
Walter Roberson
on 30 Dec 2022
triples = fread(fid, [3 NUMBER_OF_TRIPLES], 'uint8=>double') .';
Use inf for NUMBER_OF_TRIPLES if you want to read to end of file.
Each row of triples will be 3 entries, converted to double precision already -- ready for you to do calculations such as
triples(:,2) * 2^16 + triples(:,1) * 2^8 + triples(:,3)
or as appropriate depending what byte order is used for the triples.
More Answers (0)
See Also
Products
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!