dup() and dup2()(12.2)

newFD = dup( oldFD );
if( newFD < 0 ) { perror(“dup”); exit(1); }

or, to force the newFD to have a specific number:

returnCode = dup2( oldFD, newFD );

if(returnCode < 0) { perror(“dup2”); exit(1);}

• In both cases, oldFD and newFD now refer to the same file

• For dup2(), if newFD is open, it is first automatically closed

• Note that dup() and dup2() refer to fd’s and not streams

  • A useful system call to convert a stream to a fd is
    int fileno( FILE *fp );
    

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