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POstdout redirect changing output
 

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    <p>I have a program called <code>abc</code>.</p> <p>When I run the following command:</p> <pre><code>$ ./abc &lt; infile </code></pre> <p>I get the following output:</p> <pre><code>ijklm </code></pre> <p>However, when I run:</p> <pre><code>$ ./abc &lt; infile &gt; outfile $ cat outfile </code></pre> <p>I am given this output:</p> <pre><code>ijkoo </code></pre> <p>Now, I'm assuming this is a bug with my program. However, regardless of what my program is doing, I do not know how this is possible.</p> <p><strong>EDIT:</strong></p> <p>Now that I know it is possible, I'm curious as to what it is in my program that is causing this.</p> <p>There is a block inside a loop in my program that contains:</p> <pre><code>byte = ascii_to_byte(asciibyte); putchar(byte); </code></pre> <p>byte is of type <code>char</code>.</p> <p>Now if I change <code>putchar(byte)</code> to <code>printf("%c", byte)</code> all the output stays the same.</p> <p>However, if I change it to <code>printf("%d", byte)</code>, then <code>$ ./abc &lt; infile</code> outputs:</p> <pre><code>105106107111111 </code></pre> <p>Which is the decimal representation of those ascii characters as they were in <code>outfile</code>. But it's not the decimal representation of the characters as they actually appeared when they just got sent to stdout. I don't understand why there could be this difference.</p> <p><strong>EDIT #2:</strong></p> <p>If I change the printing line to <code>printf("%c\n", byte)</code>, then <code>$ ./abc &lt; infile</code> outputs:</p> <pre><code>i j k o o </code></pre> <p>This is consistent with what goes into outfile. Again, not sure what the difference is.</p> <p><strong>EDIT #3</strong></p> <p>I just tested this on a 32 bit machine, and the program works: <code>outputfile</code> contains <code>ijklm</code>. Wierd.</p> <p><strong>EDIT #4</strong></p> <p>Here is the main function:</p> <pre><code>int main() { char asciibyte[8]; char byte; int c; //Using int to avoid the EOF pitfall. long charcount = 0; while((c = getchar()) != EOF){ if(c != '0' &amp;&amp; c != '1'){ continue; } asciibyte[charcount % 8] = c; if(charcount % 8 == 7){ /*Testing revealed that at this point asciibyte does contain what it should contain, eight ASCII ones and zeros representing a byte read in from stdin*/ byte = ascii_to_byte(asciibyte); /*Print statements such as: printf("%d", byte); printf("%c\n", byte); reveal that the ascii_to_byte function works incorrectly on my 64 bit machine. However these statements: putchar(byte); printf("%c", byte); make it appear as though the function operates as it should. EXCEPT if i redirect that output to a file.*/ putchar(byte); } charcount++; } return 0; } </code></pre> <p>And here is the ascii_to_byte function:</p> <pre><code>char ascii_to_byte(char *asciibyte){ char byte; int i; for(i = 0; i &lt; 8; ++i){ if(asciibyte[7-i] == '1'){ byte = byte | (1 &lt;&lt; i); } } return byte; } </code></pre> <p><strong>FINAL EDIT</strong></p> <p>I noticed that I should have initialized byte to 0x00. Problem solved. Why am I this retarded? I'll give answer points to whoever can explain specifically how this caused the problem.</p>
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    1. COis the output always the same? if you run ./abc a couple of times, do you get the same result?
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    2. COYes, the output is consistent over multiple trials.
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    3. COwhat is the output of `./abc < infile | od -tx1`?
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