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  1. #include <unistd.h>
  2.  
  3. int main(void) {
  4.   // duplicate stdout
  5.   int duplicate = dup(1);
  6.   unsigned counter = 0;
  7.   for (; counter < 10; ++counter) {
  8.     if (counter % 2 == 0) {
  9.       // redirect IO on FD duplicate to stderr
  10.       dup2(2, duplicate);
  11.     } else {
  12.       // redirect it back to stdout
  13.       dup2(1, duplicate);
  14.     }
  15.     write (duplicate, "A ", 2);
  16.     write (1, "B\n", 2);
  17.   }
  18.   close (duplicate);
  19.   return 0;
  20. }
  21.  
Success #stdin #stdout #stderr 0s 2156KB
comments (?)
stdin
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Standard input is empty
stdout
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B
A B
B
A B
B
A B
B
A B
B
A B
stderr
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A A A A A
https://ideone.com/SfsoRL
language:
C (gcc 8.3)
created:
10 years ago
visibility:
public

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