cstringprintf

fprintf with string argument

In order to create a formatted file, I want to utilize fprintf. It must get char* parameters, but I have several string variables. How can I use fprintf?

Solution

  • The basic usage of fprintf with strings looks like this:

    char *str1, *str2, *str3;
FILE *f;
// ...

f = fopen("abc.txt", "w");
fprintf(f, "%s, %s\n", str1, str2);
fprintf(f, "more: %s\n", str3);
fclose(f);

    You can add several strings by using several %s format specifiers and you can use repeated calls to fprintf to write the file incrementally.

    If you have C++ std::string objects you can use their c_str() method to get a const char* suitable to use with fprintf:

    std::string str("abc");
fprintf(f, "%s\n", str.c_str());