C++ write to file

Question

I have a program which writes to text file.

Example in my textfile:

4 QA131 100 100 100 100 QA132 100 100 100 100 QA133 100 100 100 100 QA134 100 100 100 100

I want to write a new line which store the record and the 4 will turn into 5.

What is the method used to write to the file?

Here is my code:

void inputRecord() { Product product[101]; char FILENAME[20]; cout<<"Enter the file you want to open: "; cin>>FILENAME; ifstream read(FILENAME); if (read.is_open()) { while(read.good()) { read>>product[0].line; for(int i =0;i< product[0].line;i++) { read >>product[i].PartNumber >>product[i].initialQuantity >>product[i].quantitySold >>product[i].minQuantity >>product[i].price; } product[0].line+=1; } read.close(); } ofstream write(FILENAME); write<<product[0].line << endl; for(int i =0;i< product[0].line;i++) { write << product[i].PartNumber << '\t' << product[i].initialQuantity << '\t' << product[i].quantitySold << '\t' << product[i].minQuantity << '\t' << product[i].price << '\t' << endl; } write.close(); cout << "Inventory added successfully!" << endl; system("pause"); system("CLS"); }

I cannot write the item to the file.

I'm curious why you're writing out the entire file every time. I think it would be more efficient to append the new Product to the file, and remove the count line. Get the count inside your while{} loop, incrementing your counter with each successful record read until you reach End Of File. — Codes with Hammer
– Codes with Hammer, Commented Sep 12, 2013 at 15:18
You haven't posted the part of your program where you add the new item to the product array. Is that the part you are stuck on? — john
– john, Commented Sep 12, 2013 at 15:18
@john: I noticed that too. Based on the array declared size of 0 to 100, I'm assuming that adding a new item to the array is not the problem. But one never knows. — Codes with Hammer
– Codes with Hammer, Commented Sep 12, 2013 at 15:20
Question for the poster: When you say you cannot write the item to the file, what error message are you getting? — Codes with Hammer
– Codes with Hammer, Commented Sep 12, 2013 at 15:21
Hi buddies, sorry for misunderstood u all. My issue: no error message, i can write into file. but i cannt to input a new line. — user2747285
– user2747285, Commented Sep 12, 2013 at 15:26

andy mcevoy · Accepted Answer · 2013-09-12 15:27:55Z

you could just use fseek to solve your problem.

Here's a really simple example based this C++ reference example

#include<cstdio> int main(void) { FILE * pFile; pFile = fopen ( "test.txt" , "wb" ); fprintf(pFile,"00000\n"); // watch spacing for (int i=1; i<11; i++) { fprintf (pFile, "%d. This line a line of stuff.\n",i); } fseek(pFile , 0 , SEEK_SET ); fprintf(pFile,"10 \n"); fclose(pFile); return 0; }

@user2747285 fseek can be used in any file opened in binary mode. There's nothing to stop you writing text to a file opened in binary mode if that's what you want to do.
glad it helped. Please mark it as answered if that's the approach you used.

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