How to write multiple lines to a output file in C?

Question

I am new to file operations like write/read in C. Is there a solution to write all printf() which is below, to my output text file? After execution I was not able to write all the lines to my text file.

for(i=0;i < n;i++)
    if(i!=startnode)
    {
        outputFile = fopen(myOutputFile, "w");

        printf("\nCOST of %d = %d", i, cost[i]);
        printf("\nTRACE = %d", i);

        j=i;
        do
        {
            j=pred[j];
            printf(" %d", j);

        }
        while(j!=startnode);
    }

Yes I tried but it only prints the last calculation to my file. I need all the i and cost[i] values in my file. also j value. — xxxx, Mar 31 '16 at 10:46
use freopen(fileName,"w",stdout); instead of outputFile = fopen(myOutputFile,"w"); Then use just printf() to print in file. — Shafi, Mar 31 '16 at 10:59
You should probably put the `fopen` before the `for` loop, and put an `fclose(myOutputFile)` after the `for` loop has terminated. — Ian Abbott, Mar 31 '16 at 11:53

ckruczek · Answer 1 · 2016-03-31T10:59:33.930

3

You can use fprintf(FILE * stream, const char * format, ... ) and pass the file handle to the function.

for(i=0;i < n;i++)
    if(i!=startnode)
    {
        outputFile = fopen(myOutputFile, "a");

        fprintf(outputFile,"\nCOST of %d = %d", i, cost[i]);            
        fprintf(outputFile,"\nTRACE = %d", i);

        j=i;
        do
        {
            j=pred[j];
            fprintf(outputFile," %d", j);

        }
        while(j!=startnode);
       fclose(outputFile);
    }

Edit according to your comment:

According to your comment update the mode you are opening the file to: fopen("asdas","a")

edited Mar 31 '16 at 10:59

answered Mar 31 '16 at 10:47

ckruczek

2,361
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23

Yes I tried but it only prints the last calculation to my file. I need all the i and cost[i] values in my file. also j value in do/while statement. – xxxx Mar 31 '16 at 10:49
Appending to the file should solve the problem. Everything else is unknown in your question. You should update your question accordingly. – ckruczek Mar 31 '16 at 10:55
thanks @ckruczek it worked. But I need something to clear my file. Because when I run again it always over writes and makes complex data inside of my file. – xxxx Mar 31 '16 at 11:15
This has been answered alot. [Here](http://stackoverflow.com/questions/4815251/how-do-i-clear-the-whole-contents-of-a-file-in-c) for example. – ckruczek Mar 31 '16 at 11:17

score 0 · Answer 2 · answered Mar 31 '16 at 10:58

Try this:

outputFile = fopen(myOutputFile, "a");
for(i=0;i < n;i++)
    if(i!=startnode)
    {    
        fprintf(outputFile,"\nCOST of %d = %d", i, cost[i]);            
        fprintf(outputFile,"\nTRACE = %d", i);

        j=i;
        do
        {
            j=pred[j];
            fprintf(outputFile," %d", j);

        }
        while(j!=startnode);
    }

Shafi · Answer 3 · 2016-03-31T11:11:55.523

Try this:

freopen(myOutputFile, "a+",stdout);  //Redirect the standard output to file, "a+" - is for appending info if the file is has data before it is openned
for(i=0;i < n;i++)
{        
    if(i!=startnode)
    {
        printf("\nCOST of %d = %d", i, cost[i]);            
        printf("\nTRACE = %d", i);

        j=i;
        do{
            j=pred[j];
            printf(" %d", j);

        }while(j!=startnode);
    }
}

How to write multiple lines to a output file in C?

3 Answers3

Edit according to your comment: