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PORandom writing order to output file?
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  1. PORandom writing order to output file?
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    copied!<p>I've written a program that writes information to a file. The output to the file is not in the order that I am expecting. I have a header line and three additional lines with numerical information. The header comes first following by the third, first, and second lines. </p> <p>Note that the file is open in <code>a</code> mode, not <code>a+</code>. According to various sources, re-positioning operators like <code>fseek()</code> are suppose to be ignored. For a while I was actually getting the third line <strong><em>before</em></strong> the first line <strong><em>after</em></strong> that line was written. If the <code>fseek()</code> line is omitted, the third line actually is written before the header ..</p> <p>If the <code>fseek()</code> function is left commented (regardless of being in <code>a</code> or <code>a+</code> mode) the output is as shown in the picture below. </p> <p>I wrote in a bit of code to see how the output <em>should</em> be written. The text in the file is certainly not what it should be .. </p> <p>I attempted to use the <code>fseek()</code> function to find the position just before the EOF before each write but to no avail. </p> <p><strong>I have also noticed that if I use <code>fflush(writeP)</code> then I get the same effect that including the <code>fseek()</code> function would. The file is still out of order as shown, but the third line is no longer before the header line.</strong></p> <p>What am I missing? </p> <pre><code>void quickSortHelper(int* num, long startTime, long endTime, int size){ FILE *writeP = fopen(QUICKSORT_FILE, "a"); if(writeP == NULL){ fputs("Error opening file\n", stderr); exit(1); } static int times = 0; long deltaT; //change in time if(size &lt; STEPSIZE){//first time, write header to file printf("Writing header!\n"); fprintf(writeP, " --- QUICKSORT ---\nCOUNT\tTIME\tMEDIAN\n"); } deltaT = (clock() - startTime)/(CLOCKS_PER_SEC/1000); //fflush(writeP); fseek(writeP, -1, SEEK_END); printf("Writing: %d\t%ld\t%d\n", size, deltaT, findMedian(num, size)); fprintf(writeP, "%d\t%ld\t%d\n", size, deltaT, findMedian(num, size)); if(++times == 3) fclose(writeP); return; </code></pre> <p>}</p> <p><img src="https://i.stack.imgur.com/FOpbz.jpg" alt="enter image description here"></p> <p>With the <code>fseek()</code> line commented, the output is:</p> <p><img src="https://i.stack.imgur.com/RUJ5Q.jpg" alt="enter image description here"></p>
 

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