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  1. #include <stdexcept>
  2. #include <string>
  3. #include <iostream>
  4. #include <thread>
  5.  
  6. #include <unistd.h>
  7.  
  8. void reader(std::string& out, int fd)
  9. {
  10.     char buf[1024];
  11.     int rnum = 0;
  12.     do {
  13.         rnum = read(fd, buf, 1024);
  14.         if (rnum > 0) {
  15.             out.append(buf, rnum);
  16.         }
  17.     } while (rnum > 0);
  18. }
  19.  
  20. void exec(const std::string& cmd, const std::string& in,
  21.         std::string& out, std::string& err)
  22. {
  23.     int outfd[2];
  24.     int infd[2];
  25.     int errfd[2];
  26.  
  27.     // Where the parent is going to write to
  28.     if (pipe(infd) != 0)
  29.         throw std::runtime_error("failed to create a pipe");
  30.  
  31.     // From where parent is going to read
  32.     if (pipe(outfd) != 0)
  33.         throw std::runtime_error("failed to create a pipe");
  34.     if (pipe(errfd) != 0)
  35.         throw std::runtime_error("failed to create a pipe");
  36.  
  37.     if (fork()==0) {
  38.         close(STDOUT_FILENO);
  39.         close(STDIN_FILENO);
  40.         close(STDERR_FILENO);
  41.  
  42.         dup2(infd[0],  STDIN_FILENO);
  43.         dup2(outfd[1], STDOUT_FILENO);
  44.         dup2(errfd[1], STDERR_FILENO);
  45.  
  46.         close(outfd[0]); // Not required for the child
  47.         close(outfd[1]);
  48.         close(infd[0]);
  49.         close(infd[1]);
  50.         close(errfd[0]);
  51.         close(errfd[1]);
  52.  
  53.         execl("/bin/bash", "bash", "-c", cmd.c_str(), 0);
  54.         exit(0);
  55.     } else {
  56.         //close unused file descriptors
  57.         close(infd[0]);
  58.         close(outfd[1]);
  59.         close(errfd[1]);
  60.  
  61.         //create some threads to write to in[1] and read from out[0] err[0]
  62.         std::thread write_in(write, infd[1], in.c_str(), in.size());
  63.         std::thread read_out(reader, std::ref(out), outfd[0]);
  64.         std::thread read_err(reader, std::ref(err), errfd[0]);
  65.  
  66.         write_in.join();
  67.         read_out.join();
  68.         read_err.join();
  69.  
  70.         close(infd[1]);
  71.         close(outfd[0]);
  72.         close(errfd[0]);
  73.     }
  74. }
  75.  
  76. int main()
  77. {
  78.     std::string out, err;
  79.     exec("ls", "", out, err);
  80.     std::cout << out;
  81. }
  82.  
  83.  
Runtime error #stdin #stdout 0s 4200KB
comments (?)
stdin
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Standard input is empty
stdout
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Standard output is empty
https://ideone.com/8BHdm6
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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