Simple file processig problem

I have a text file in which the data is like this:
SHANGHAI 13831900
ISTANBUL 13120596
KARACHI 12991000
DELHI 12565901
...
It goes on like this with city names and populations. I want to have such a code that it will assign every city and population to a certain element of the array A[] after it reads the file. That is, then I want to have this:
A[0]=SHANGHAI
A[1]=13831900
A[2]=ISTANBUL
A[3]=13120596
...
I could only do the reading file part like this:

Code:

---

  FILE * fPtr;
  fPtr = fopen("POPULATIONS.TXT", "r");

---

What should I do next, please could you help?

Use fgets to read each line of text. Use sscanf to read from the line you just read or use strtok to tokenize it.

And I doubt you want one array that has both words and numbers in it. Maybe you want an array of structs? Or perhaps two parallel arrays, one of words and one of numbers?

Quote:

---

Originally Posted by tabstop

And I doubt you want one array that has both words and numbers in it. Maybe you want an array of structs? Or perhaps two parallel arrays, one of words and one of numbers?

---

Actually I want an array of structs . I want to have one like this:

Code:

---

struct City
{
char CityName[50];
double Population;
};

---

But I don't know how to do it. How can I assign every city and population to the array of struct from the file?

Quote:

---

Originally Posted by farukyaz

But I don't know how to do it. How can I assign every city and population to the array of struct from the file?

---

By reading them in, using any of your favorite reading-from-file functions (fscanf or fgets). If you know that none of your cities will contain a space, you can use the slightly-easier fscanf, otherwise as claudiu says you should read a line with fgets then split it up.

I'll go with fscanf. Thanks a lot!!!

Quote:

---

Originally Posted by farukyaz

I have a text file in which the data is like this:
SHANGHAI 13831900
ISTANBUL 13120596
KARACHI 12991000
DELHI 12565901
...
It goes on like this with city names and populations. I want to have such a code that it will assign every city and population to a certain element of the array A[] after it reads the file. That is, then I want to have this:
A[0]=SHANGHAI
A[1]=13831900
A[2]=ISTANBUL
A[3]=13120596
...
I could only do the reading file part like this:

Code:

---

  FILE * fPtr;
  fPtr = fopen("POPULATIONS.TXT", "r");

---

What should I do next, please could you help?

---

The very next thing you should do in situations like this is consult your compiler and library documentation and try to find suitable commands... The web is the last place you should try.

After problem analysis, the second most important skill a programmer can have is "looking stuff up".

Quote:

---

Originally Posted by CommonTater

The very next thing you should do in situations like this is consult your compiler and library documentation and try to find suitable commands... The web is the last place you should try.

After problem analysis, the second most important skill a programmer can have is "looking stuff up".

---

Yes, but after being directed from here too I found fscanf the most suitable command, but I just don't know how to use it and I couldn't find enough information on the internet either so that's the exact point I need help in..

Quote:

---

Originally Posted by farukyaz

Yes, but after being directed from here too I found fscanf the most suitable command, but I just don't know how to use it and I couldn't find enough information on the internet either so that's the exact point I need help in..

---

1) Since there are differences in implementation between various compilers you need to get a copy of your compiler's specific documentation to use as a reference text. If you can't find it... find a compiler that IS documented. (Personally I think Pelles C has the best help file I've ever seen)

2) scanf - C++ Reference <-- click the red text.

3) Given your file sample, I'd try something like...

Code:

---

struct City
{ char CityName[50];
  int Population;   
 } CityRec;


// then in your input loop

fscanf("%49s %d", CityRec.CityName, &CityRec.Population);

---

If you backtrack that into the fscanf() and scanf() documentation you should be able to see how it woks...

Quote:

---

Originally Posted by CommonTater

1) Since there are differences in implementation between various compilers you need to get a copy of your compiler's specific documentation to use as a reference text. If you can't find it... find a compiler that IS documented. (Personally I think Pelles C has the best help file I've ever seen)

2) scanf - C++ Reference <-- click the red text.

3) Given your file sample, I'd try something like...

Code:

---

struct City
{ char CityName[50];
  int Population;   
 } CityRec;


// then in your input loop

fscanf("%49s %d", CityRec.CityName, &CityRec.Population);

---

If you backtrack that into the fscanf() and scanf() documentation you should be able to see how it woks...

---

The link was helpful, thanks. And your code seems like what I want, if I can figure out the for loop I will use it. Here I have 81 cities and 81 corresponding populations in my POPULATIONS.TXT file. So I tried sth like this;

Code:

---

for(i=1; i<=81; i++)

---

Now I need to put the fscanf under the loop but how can I do it since there is not a loop counter "i" in fscanf? All I've read about were a few fcanf commands without a need for a loop.

It seems to me like you have no idea how to use arrays whatsoever, otherwise it should become clear that "i" will be the index of your structure array.

Quote:

---

Originally Posted by claudiu

It seems to me like you have no idea how to use arrays whatsoever, otherwise it should become clear that "i" will be the index of your structure array.

---

I know arrays very well but I wasn't sure about an array of struct, and because my compiler still gives a lot of errors I had to ask it.

First if you are getting errors you don't understand, no, you don't know arrays very well at all...

Based on my previus example...

Code:

---

typedef struct City
{ char CityName[50];
  int Population;   
 };

// create the array...
int CitiesSize = 10;
City Cities = malloc(CitiesSize * sizeof(City));

// open your file
CityFile = fopen(filename,"r");

// initialize a counter
int CityCount = 0;
// read your file
while ( fscanf(CityFile, "%49s %d", Cities[CityCount].CityName, &Cities[CityCount].Population))
  { CityCount++;

    // manage the array
    if (CityCount > CitiesSize)
      {CitiesSize += 10;
        Cities = realloc( Cities,CitiesSize * sizeof(City); } }

// close the file
fclose(CityFile);

printf("%d Cities loaded\n",CityCount);

---

That will read the file, no matter how many cities, up to the limit of memory.

Thanks a lot! I understand all you suggested.
By the way yes I know arrays very well, as long as it's only array.