Libxlsxwriter: A C library for creating Excel XLSX files.

Libxlsxwriter is a C library that can be used to write text, numbers, formulas and hyperlinks to multiple worksheets in an Excel 2007 XLSX file.

It supports features such as:

• 100% compatible Excel XLSX files.
• Full Excel formatting.
• Merged cells.
• Defined names.
• Autofilters.
• Charts.
• Data validation and dropdown lists.
• Conditional formatting.
• Worksheet PNG/JPEG/GIF images.
• Cell comments.
• Support for adding Macros.
• Memory optimization mode for writing large files.
• Source code available on GitHub.
• FreeBSD license.
• ANSI C.
• Works with GCC, Clang, Xcode, MSVC 2015, ICC, TCC, MinGW, MingGW-w64/32.
• Works on Linux, FreeBSD, OpenBSD, OS X, iOS and Windows. Also works on MSYS/MSYS2 and Cygwin.
• Compiles for 32 and 64 bit.
• Compiles and works on big and little endian systems.
• The only dependency is on zlib.

Here is an example that was used to create the spreadsheet shown above:

#include "xlsxwriter.h"

int main() {

    /* Create a new workbook and add a worksheet. */
    lxw_workbook  *workbook  = workbook_new("demo.xlsx");
    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);

    /* Add a format. */
    lxw_format *format = workbook_add_format(workbook);

    /* Set the bold property for the format */
    format_set_bold(format);

    /* Change the column width for clarity. */
    worksheet_set_column(worksheet, 0, 0, 20, NULL);

    /* Write some simple text. */
    worksheet_write_string(worksheet, 0, 0, "Hello", NULL);

    /* Text with formatting. */
    worksheet_write_string(worksheet, 1, 0, "World", format);

    /* Write some numbers. */
    worksheet_write_number(worksheet, 2, 0, 123,     NULL);
    worksheet_write_number(worksheet, 3, 0, 123.456, NULL);

    /* Insert an image. */
    worksheet_insert_image(worksheet, 1, 2, "logo.png");

    workbook_close(workbook);

    return 0;
}

See the full documentation for the getting started guide, a tutorial, the main API documentation and examples.