File appending

Hello!

I had a question about appending data in to a file.

My program flows in the following way--

Code:

// This function reads data from the file
parse_input_data_for_one_algo(some parameters) 
{
FILE *f = fopen (filename, "rw+");
while ( fgets (in_line, 100, f) != NULL )
{
//read values
}
fclose(f);
}

Code:

parse_input_data_for_second_algo(some parameters) 
{
FILE *f = fopen (filename, "rw+");
while ( fgets (in_line, 100, f) != NULL )
{
//read values
}
fclose(f);
}

Code:

// Call to both parse functions in another file which contains the main program
int main(int argc, char **argv)
{
char *filename = argv [1];
parse_input_data_for_one_algo (filename,some parameters);
//Algorithm-1
char *filename1 = argv [1];
parse_input_data_for_second_algo (filename1,some parameters);
//Algorithm-2
}

My text file is in the following format--

x 12 44
y 3 1
y 1 2 -1
z 1 2 1
z 3 1 2
z 4 1 3
z 6 1 4
t 1 2 1 2 1
t 1 2 3 1 2
t 1 3 4 1 1

I am trying to write additional data from the main file after "Algorithm-1" is solved, in to the text file after all the "z" s

So my new text file with appended data would look like this --
(1,2,6,9 have been appended to the file)

x 12 44
y 3 1
y 1 2 -1
z 1 2 1 1
z 3 1 2 2
z 4 1 3 6
z 6 1 4 9
t 1 2 1 2 1
t 1 2 3 1 2
t 1 3 4 1 1

The new appended text file would now be read by parse_input_data_for_second_algo.
Kindly let me know of alternatives of how I could solve this problem.

Thanks in advance!

AFAIK, you're stuck with basically writing a new file, deleting the old one and renaming the new one to match the old filename

Read data from text file into a buffer; filter line that contains "z"; append main file data into buffer that holds the "z" line.