CODEWITHSUNDEEP
cfileprintftext-files
Mr Guliarte
Mr Guliarte

Reputation: 739

Writing in a Text File

So, I have this code:

#include <stdio.h>


  int main(int argc, char *argv[]){
        FILE *ReadFile, *WriteFile;
        float key;
        int quantKeys,T;

        int i;

        /* errors verification */

        if (argc < 3){
            printf(" Use the correct entry parameters.\n");
            exit(1);
        }

        if((ReadFile = fopen(argv[1],"rw")) == NULL){
            printf("Error when trying to open the file\n");
            exit(1);
        }

        if((WriteFile = fopen(argv[2],"rw")) == NULL){
            printf("Error when trying to open the file.\n");
            exit(1);
        }

        /* main code */

        quantKeys = 45658;
        T = 5;

        fprintf(WriteFile,"%d",T);
        fprintf(WriteFile,"%d",quantKeys);
        fclose(ReadFile);
        fclose(WriteFile);

    return 0;
    }

All I want to do is write the variables "quantChaves" and "T" in a text file, that I pass as the third parameter of the main function. It compiles and runs with no problems, but my text file keeps empty after I run it. What I am doing wrong?

Upvotes: 1

Views: 127

Answers (2)

Nanc
Nanc

Reputation: 464

If you want to write in a file you should use

  • w : Create an empty file
  • w+ : Create an empty file and open it for update
  • r+ : Open a file for update
  • a+ : Open a file for update with all output operations writing data at the end of the file
    not rw. You can read more about fopen.

Upvotes: 1

Mike Precup
Mike Precup

Reputation: 4218

rw isn't a valid mode for fopen. If you want to write, you can use w, w+, r+, or a+. Full details are in your man pages, or here.

The gist of the differences:

w doesn't allow reading

r+ doesn't create a new file if it doesn't exist

a+ appends the text instead of overwriting the file contents.

Upvotes: 6

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