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PORead and write struct with unistd.h read/write
 

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  1. PORead and write struct with unistd.h read/write
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    <p>I'm studying UNIX programming and was experimenting with read/write system calls. I have a file with a pair of integer:</p> <pre><code>4 5 </code></pre> <p>and I wrote this code to read the numbers:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;unistd.h&gt; #include &lt;sys/stat.h&gt; #include &lt;fcntl.h&gt; typedef struct prova { int first; int second; } prova_t; int main(void) { int fd; prova_t origin; prova_t result; ssize_t bytes_read; size_t nbytes; fd = open("file.bin", O_WRONLY | O_CREAT); origin.first = 24; origin.second = 3; write(fd, &amp;origin, sizeof(prova_t)); close(fd); fd = open("file.bin", O_RDONLY); nbytes = sizeof(prova_t); /* 1.BAD */ bytes_read = read(fd, &amp;result, nbytes); write(STDOUT_FILENO, &amp;(result.first), sizeof(int)); write(STDOUT_FILENO, &amp;(result.second), sizeof(int)); close(fd); /* 2.GOOD */ nbytes = sizeof(int); bytes_read = read(fd, &amp;(result.first), nbytes); write(STDOUT_FILENO, &amp;(result.first), bytes_read); bytes_read = read(fd, &amp;(result.second), nbytes); write(STDOUT_FILENO, &amp;(result.second), bytes_read); return 0; } </code></pre> <p>In my first attempt I tried to read the whole struct from file and write its members to stdout. In this way, along with the numbers, I get some weird characters</p> <pre><code>4 5 E�^� </code></pre> <p>In my second attempt I read the numbers one by one and there were no problems in the output.</p> <p>Is there any way to read and write the struct using the first method?</p> <p><em>Edit: I updated the code to reflect suggestion from other users but still getting strange characters instead of numbers</em></p>
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    1. CODeadMG is right, but I am wondering if there might not be another aspect: does your input file contain the text "4 5", or is it a binary file holding the numbers 4 and 5 in binary form?
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    2. COReading other suggestions I tried writing the struct on file using write and reading it back, but the problem persist. I updated my code
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