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How to read an Excel file

This is a discussion on How to read an Excel file within the C++ Programming forums, part of the General Programming Boards category; I have a work: that how to read an microsoft excel file. For example: I have an excel file with ...

  1. #1
    hqt
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    Question How to read an Excel file

    I have a work: that how to read an microsoft excel file.
    For example: I have an excel file with multi sheets. (that I don't know what does these sheets' name). And my work is:
    1) how to scan this file to find what sheets does it have and what's name.
    2) after that, I want to read an exact cell that I want. for example: I want to read <programming sheet><cell A93>.

    I think this work need a library to work, and I don't know it. I play with algorithm very much, but I never do something like that before. So, who can help me, please

    thanks for all

  2. #2
    C++ Junkie Mozza314's Avatar
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    Not sure how you would do this directly. However you can save excel files with a single sheet to .csv, which would convert a sheet that looks like this:

    Code:
    +---+---+
    | 1 | 2 |
    +---+---+
    | 3 | 4 |
    +---+---+
    to a .csv file with these contents

    Code:
    1,2
    3,4
    For multiple sheets, you could write something in excel vba that would save each sheet to a separate .csv file, and then use your C++ program on those files. It's been a while since I used vba though, but I do know it's possible and fairly simple.

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    hqt
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    Question

    I have googled and see that there're some ways, but they have a same method: convert excel file to cvs file.
    So, we cannot use excel file directly, huh :-?

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    C++ Junkie Mozza314's Avatar
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    Well, it must be possible, but I'm guessing it'd be pretty complex unless there's some library out there. Why do you want to use the excel file directly?

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    &TH of undefined behavior Fordy's Avatar
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    Quote Originally Posted by hqt View Post
    I have googled and see that there're some ways, but they have a same method: convert excel file to cvs file.
    So, we cannot use excel file directly, huh :-?
    Yes you can, but you will probably need to use COM.
    Here's an example c++ for excel worksheets

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    hqt
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    I have convert an excel file to cvs file, After open by notepad and see that, to express each cell, excel use "," this very hard to use algorithm to process these cells.
    And, I google and no answer tell me how to convert excel file with multi sheets to multi cvs file by C++. So, who can help me, please

    thanks

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    how to convert excel file with multi sheets to multi cvs file by C++.
    You would probably be better off using Excel to export each sheet to a separate file. Trying to read an Excel file with C/C++ is difficult for several reasons. The first reason is that there are different versions of the file format depending on which version of Excel is being used.
    I have convert an excel file to cvs file, After open by notepad and see that, to express each cell, excel use "," this very hard to use algorithm to process these cells.
    Actually processing a Comma Separated Values file is fairly straight forward, as long as the actual data does not contain commas. Read the line with getline() to get the entire line into a std::string. Then using stringstreams use getline(), with the third parameter, or use the extraction operator<< to extract the data, using a throw away character to dispose of the comma.

    If you feel you must convert the actual Excel file with C/C++ you may want to start by studying this: Excel File Format.

    Jim
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  8. #8
    hqt
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    You would probably be better off using Excel to export each sheet to a separate file. Trying to read an Excel file with C/C++ is difficult for several reasons. The first reason is that there are different versions of the file format depending on which version of Excel is being used.
    Ohh, this make me sad and disappointed, because I always think C/C++ can do everything
    I have convert an excel file to cvs file, After open by notepad and see that, to express each cell, excel use "," this very hard to use algorithm to process these cells.
    Oh, I have use this way: convert the cvs file to two demension vector of string. And, we suppose excel table like two demension array. But, I see some problems with my solution. The most evident is very slow !!! Copy a table to array take a lot of time, huh
    @: I still like use directly excel file. Like above suggest and some source I have googled that use Visual C++. But, they say you must know COM application... and their code make me dizzy @@. My deadline is going to end up, so I hardly to learn a very new thing now. So, how to use this method in an esier way ?

    So, who has a new idea, please teach me.
    thanks
    Last edited by hqt; 11-09-2011 at 09:18 AM.

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    Registered User manasij7479's Avatar
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    Quote Originally Posted by jimblumberg View Post
    Actually processing a Comma Separated Values file is fairly straight forward, as long as the actual data does not contain commas. Read the line with getline() to get the entire line into a std::string. Then using stringstreams use getline(), with the third parameter, or use the extraction operator<< to extract the data, using a throw away character to dispose of the comma.
    Wouldn't using getline directly with ',' specified as the delimiter be simpler ?
    Manasij Mukherjee | gcc-4.8.2 @Arch Linux
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    Wouldn't using getline directly with ',' specified as the delimiter be simpler ?
    If you are trying to get numeric values you must still convert the string to the numeric values. Yes you can do all the processing on the file stream but I find string stream errors easier to handle than file stream errors, so I prefer to use getline() to get an entire line from the file then process that line using string streams.


    Jim

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    Registered User manasij7479's Avatar
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    Quote Originally Posted by jimblumberg View Post
    If you are trying to get numeric values you must still convert the string to the numeric values.
    If different data types are there.... a much better approach could be use some database library...which would surely have ways to read in csv `s into relations.
    string stream errors easier to handle than file stream errors
    Agreed...
    Wondering how viable it is to pull the whole thing into a string stream..and using >>s for getting the data..(and making a custom manipulator to ignore the comma)
    Last edited by manasij7479; 11-09-2011 at 12:36 PM.
    Manasij Mukherjee | gcc-4.8.2 @Arch Linux
    Slow and Steady wins the race... if and only if :
    1.None of the other participants are fast and steady.
    2.The fast and unsteady suddenly falls asleep while running !



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    a much better approach could be use some database library
    Possibly, but in my opinion at the cost of much higher complexity. And no matter what the programmer must know what each data element represents.

    Wonder how viable is pulling the whole thing into a string stream..and using >>s for getting the data..(and making a custom manipulator to ignore the comma)
    Again, possible as long as the file size does not exceed the string stream maximum size. In my opinion using this method only becomes reasonable if profiling determines a need for a different approach, and then only if you are going to be parsing this data source quite often.

    Jim

  13. #13
    chococoder
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    Quote Originally Posted by hqt View Post
    Ohh, this make me sad and disappointed, because I always think C/C++ can do everything
    And with enough time, perseverance, and budget you probably can

    After all, Excel itself was written (largely) in C and C++, so no reason you can't do the same, in theory.
    Whether it is practical is of course another matter entirely.

    A quick search of the internet found several libraries that claim to be able to handle XLS documents .
    C++ Excel Library to read/write xls/xlsx files - LibXL
    C++ Library For Direct Writing Excel Spreadsheets | PRLog
    C++ Library for Excel

    These are commercial products. The first several pages of search results didn't yield an open source or otherwise free library (except one announcement from 2 years ago stating someone's starting one, but that one died already).

  14. #14
    and the hat of wrongness Salem's Avatar
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    I suppose with some digging (OK, make that a lot of digging), you might find something in the source code for Home LibreOffice
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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