• Well, the problem was solved today.

Since "testAll.csv" is generated by Java/Eclipse, and I noticed that the LineSeperator is "\r", so I just need to assign RecordSeperator->"\r".

here is the sample file


I get 775108 which is right.

However when I'm trying:


I get 768065 which is the incorrect line number, and StringSplit couldn't keep all lines with right column number, ie length1 is not the same as length2.

I also tried to partition the file into 100 files[by Export], and ReadList works correctly!

Additionally, I've changed the .csv file to a .txt file, ReadList works well.

And I found another thing is: when I export the fList=Import["testAll.csv","Lines"]; as 'testAll_new.csv'.

Then ReadList["testAll_new.csv","Records"]; is right...

I found without right options, Import function also has the similar problem in auto parsing the file.

enter image description here

  • 2
    $\begingroup$ You need to provide the file or an example that shows the problem or no one here can really help. $\endgroup$
    – Ymareth
    Nov 20, 2014 at 9:40
  • $\begingroup$ You probably need to specify the correct RecordSeparator-s. It might be that your file contains a couple of them. $\endgroup$ Nov 20, 2014 at 10:07
  • $\begingroup$ @SjoerdC.deVries strange, I found ReadList the new .csv file Generated by Import and Export by Mathematica is OK... $\endgroup$ Nov 20, 2014 at 10:19
  • $\begingroup$ Is there a typo in your new edit ("lines" instead of "Lines")? $\endgroup$ Nov 20, 2014 at 10:21

1 Answer 1


Possible cause:

 f = OpenWrite["test.csv"];
 WriteString[f, "1,2,3\n\n4,5,6\n"];

enter image description here

 Through[{Length, MatrixForm}@Import["test.csv", "Lines"]]
 Through[{Length, MatrixForm}@ReadList["test.csv", "Record"]]

enter image description here

Readlist doesn't count a blank line (double line ending) as a "record" while Import does

You can fix this with the option NullRecords -> True to ReadList

Interestingly if you have extra returns at the end of the file WriteString[f, "1,2,3\n\n4,5,6\n\n\n\n"]; Import ignores those, while ReadList[...,NullRecords->True] picks them up. The "Lines" import format does not seem to be documented by the way.

(note with the plural "Records" I get "Records is not a valid format specification" )

  • $\begingroup$ I found my line seperator is "\r" that's the cause... $\endgroup$ Nov 21, 2014 at 1:50

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