Thread: Saving each line of a file

Hi,

I have a txt file with some specifications on building a grid map. The file has already been opened in a FILE stream, but I'm having some difficulty trying to sort of extract the contents of the file stream (line-by-line).

Example:

Code:

2
2
1 2 4 2 2 2
2 1 4 2 2 3
2 2 4 2 2 1

This is saying I have a 2x2 grid map, with 2 tracks per path (or channel). The remaining three strings of numbers are basically description of element placements on the 2x2 map. Example: 1 2 4 2 2 2 says element (1,2) has outlet 4 connected to inlet 2 of element (2,2). This file can of course have hundreds of such lines describing element placement.

So my problem is that I need to have each line and convert that string to an integer; save it somewhere so it can be referenced for building the grid map when the praising of the file is finished.

Thank you.

Post up your code for this, and tell us what the specific problem is.

Sure, we could code it up for you, but you won't learn anything by that (and we'll be buried 20 meters in such requests, in no time.)

So help us avoid becoming "free programming central", and help yourself, all at the same time. Try it!

I'm putting it in a while loop as follows:

Code:

while(fgets(buff, sizeof (buff), netlist) != NULL)

I wanted to place something like strtoul(buff, NULL, 10) in the while loop, but it only converts the first number of each line.
I'm unsure how to implement it using sscanf(). In particular because the lines are not always of constant size. The first two lines is one character each, while the remaining lines are 6 characters each.

Okay, so here is how I see it. fgets() reads one line at a time. Therefore, it has to loop N times to get to line N. So my first two lines each have one characters. In my first while loop, I only loop once to get the first line.

Code:

while (i<1)
	{
		fgets(buff, sizeof (buff), file_stream);
		puts(buff);
		sscanf(buff, "%d", &a);
		printf("grid is %d\n", a);
		i++;
	}

The weird thing is that puts() has no output (a blank line) and the value stored from sscanf() is 0.

There can be as much as 4000 lines of these guys (6 digits). Compiler is GCC on Linux and lets say we are designing for 1GB (worst case). I have 3BG, but then I have to build the map, and run an algorithm on it, so I will need the rest.

Originally Posted by strange

Is buff a pointer? If so, then sizeof(buff) will return sizeof(char *) . . . probably not what you want.

Beyond that, that snippet looks fine to me . . .

buff is actually declared as:
char buff[100];

Well here is some self discovery I made:

I have two while loops now. They are the same as that posted in post #6. They only thing that changes is the variable that sscanf() uses. But in order to get to the second line, I only looped once in the second while loop and not twice as I had first thought. Also, before doing any looping I have a line that prints out the contents of the txt file to stdout. When this line is compiled with the code, sscanf() always stores a value of 0 for both lines. When it is commented out, it works as just described. Are these behaviors normal that I am experiencing?

You can get ALL your 6 numbers with one line, using sscanf(), and you should do that.

not one %d, use six %d's, all in the same line.

Try using the stack with your compiler and see if it will give you the memory for that large array:

int numbers6[4000][6];

If that doesn't work, we'll use calloc() and get the memory from the heap part of memory.

I seem to be making some progress. The first two lines are saved. Now I'm tackling the lines with 6 characters. I'm using an infinite for() loop:

Code:

for(;;)
		{
			fgets(buff, sizeof (buff), file_stream);
			sscanf(buff, "%d %d %d %d %d %d", &a,&b,&c,&d,&e,&f);
			printf("first row is %d %d %d %d %d %d\n", a,b,c,d,e,f);
			if(a == -1) break;
		}

I can see two issues here. The first one is how am I to store all the characters of each line so they can be accessed in the future. And the second one is, I really dont need the "-1" row to build my map, I just included it there for testing to break the for() loop. But it still gets saved. I would like to avoid that.

Originally Posted by Adak

You can get ALL your 6 numbers with one line, using sscanf(), and you should do that.

not one %d, use six %d's, all in the same line.

Try using the stack with your compiler and see if it will give you the memory for that large array:

int numbers6[4000][6];

If that doesn't work, we'll use calloc() and get the memory from the heap part of memory.

Thats quite a lot of memory, especially since I will be running the program over-and-over for testing. Would I have to do anything special in terms of mem management to free up that memory when the program is finished?