print2fp(const void *buffer, size_t size, FILE *stream) {
if(fwrite(buffer, 1, size, stream) != size)
return -1;
return 0;
}
How to write the data into string stream instead of File stream?
There is a very neat function in the posix 2008 standard: open_memstream(). You use it like this:
char* buffer = NULL;
size_t bufferSize = 0;
FILE* myStream = open_memstream(&buffer, &bufferSize);
fprintf(myStream, "You can output anything to myStream, just as you can with stdout.\n");
myComplexPrintFunction(myStream); //Append something of completely unknown size.
fclose(myStream); //This will set buffer and bufferSize.
printf("I can do anything with the resulting string now. It is: \"%s\"\n", buffer);
free(buffer);
Use sprintf
: http://www.cplusplus.com/reference/cstdio/sprintf/
Here's an example from the reference:
#include <stdio.h>
int main ()
{
char buffer [50];
int n, a=5, b=3;
n = sprintf(buffer, "%d plus %d is %d", a, b, a+b);
printf("[%s] is a string %d chars long\n", buffer, n);
return 0;
}
Output:
[5 plus 3 is 8] is a string 13 chars long
Update based on recommendations in comments:
Use snprintf
as it is more secure (it prevents buffer overflow attacks) and is more portable.
#include <stdio.h>
int main ()
{
int sizeOfBuffer = 50;
char buffer[sizeOfBuffer];
int n, a = 5, b = 3;
n = snprintf(buffer, sizeOfBuffer, "%d plus %d is %d", a, b, a+b);
printf ("[%s] is a string %d chars long\n", buffer, n);
return 0;
}
Notice that snprintf
's second argument is actually the max allowed size to use, so you can put it to a lower value than sizeOfBuffer
, however for your case it would be unnecessary. snprintf
only writes sizeOfBuffer-1
chars and uses the last byte for the termination character.
Here is a link to the snprintf
documentation: http://www.cplusplus.com/reference/cstdio/snprintf/
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