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POWrite data to pipe C++
 

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  1. POWrite data to pipe C++
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    <p>i need to do something like</p> <pre><code>echo "data" | cat </code></pre> <p>Using </p> <pre><code>echo "data" | my program </code></pre> <p>And inside my program calls the cat and sends my stdin to the cat stdin and get the stdout from the cat.</p> <p>I already fork the process, close the write and the read, dup2 them and execl.. So i can get the stdout from it, if i do one execl("/bin/sh", "sh", "-c", "ls -lahtr", NULL) i can get the file list as the output.</p> <p>but i don't know how to send data, like send the echo data that i read from my stdin and send to the execl("/bin/sh", "sh", "-c", "cat", NULL) stdin and return my echo string.</p> <pre><code>#include &lt;stdlib.h&gt; #include &lt;stdio.h&gt; #include &lt;unistd.h&gt; #include &lt;sys/stat.h&gt; #include &lt;fcntl.h&gt; #include &lt;sstream&gt; #include &lt;iostream&gt; using namespace std; int main() { int ficheiro_fd; int pipe_fd[2]; char buffer[20]; int num_bytes; pipe(pipe_fd); switch ( fork() ) { case -1: exit(1); case 0: close(pipe_fd[1]); dup2(pipe_fd[0], 0); execlp("/usr/bin/base64"," ", NULL); break; default: close(pipe_fd[0]); //ficheiro_fd = open("output.txt", O_RDONLY); while ((num_bytes = read(fileno(stdin), buffer, 1)) &gt; 0){ write(pipe_fd[1], buffer, num_bytes); } close(pipe_fd[1]); wait((int*)getpid()); } return 0; } </code></pre> <p>With this code i can send some data to the program and it writes on the screen, i want to know how i can get the stdout and send to one variable. Thanks for the help ppl.</p>
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    1. USTom van der Woerdt
    1. USLefsler
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      1. VTUpMod
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      1. VTUpMod
    1. COIt seems like you're doing something completely useless. Please show some code.
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      1. USFred Foo
    2. COCan you share your code? your question is a bit convoluted. In general a pipe is only one way, one process reads while the other writes, you cannot send data from the reader back to the writer over the same pipe. So you can do echo data | your_prog | cat ... which will pass your program's stdout to cat's stdin...
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      1. USAhmed Masud
    3. COHi i shared the code, the reason i need that is i'm going to send one command trought socket and i need to process on the other side with my input and get the return.
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      1. USLefsler
 

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