CODEWITHSUNDEEP
c++io
George Lazu
George Lazu

Reputation: 301

Write formatted text to file - C++

I have this code:

        printf("GPU: %ic  SYSTEM: %ic  CPU: %ic  HDD: %ic  ",temp[0],temp[1],temp[2],temp[7]);
        ofstream temp_file;
        temp_file.open("D:\\localhost\\xampp\\htdocs\\monitor\\temps.json");
        temp_file << fprintf("\"{\"GPU\": [%ic], \"System\": [%ic], \"CPU\": [%ic], \"HDD\": [%ic]}\"", temp[0],temp[1],temp[2],temp[7]);
        temp_file.flush();
        temp_file.close();

and I get the error "cannot convert 'const char*' to 'FILE* {aka _iobuf*}' for argument '1' to 'int fprintf(FILE*, const char*, ...)'

the temp variable is an int, and the first line of the code does successfully print out the formatted text. How do i push that text to a file?

Upvotes: 0

Views: 8482

Answers (4)

Jorg B Jorge
Jorg B Jorge

Reputation: 1109

The first parameter of fprintf must be the pointer to a FILE object that identifies the stream instead of temp[0] (GPU).

The C library function int fprintf(FILE *stream, const char *format, ...) sends formatted output to a stream.

Upvotes: 0

Andrew Henle
Andrew Henle

Reputation: 1

You are misusing fprintf().

fprintf() returns an int and expects its first argument to be a FILE *, per the documentation:

int fprintf(FILE *restrict stream, const char *restrict format, ...);

You need to format your text first using s[n]printf() if that's the route you want to take - making a C-style string and writing it to a C++ ofstream:

char buffer[ BUF_SIZE ];
snprintf( buffer, sizeof( buffer ),
    "\"{\"GPU\": [%ic], \"System\": [%ic], \"CPU\": [%ic], \"HDD\": [%ic]}\"",
    temp[0], temp[1], temp[2], temp[7] );

...

temp_file << buffer;

...

There are many other ways to format output in C++, too.

Upvotes: 1

Nim
Nim

Reputation: 33655

Use boost::format:

cout << boost::format("\"{\"GPU\": [%1%], \"System\": [%2%], \"CPU\": [%3%], \"HDD\": [%4%]}\"") % temp[0] % temp[1] % temp[2] % temp[3];

Upvotes: 1

Jesper Juhl
Jesper Juhl

Reputation: 31465

This temp_file << fprintf("\"{\"GPU\": [%ic], \"System\": [%ic], \"CPU\": [%ic], \"HDD\": [%ic]}\"", temp[0],temp[1],temp[2],temp[7]); is wrong. You cannot combine ofstream and fprintf - use one or the other.

To write formatted output to a stream you use io manipulators and you don't need to do anything special to output integers, strings, doubles etc.

Upvotes: 0

Related Questions