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Implementation of dup2

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# 8  
Old 01-25-2011
Quote:
Originally Posted by homeboy
pls tell me some detail about that.I did't figure out some method to use "st_mode" to tell whether the fd is opened.Thanks a lot.
Just look at the return code. All system calls return -1 if they fail and they set errno. If you fstat an fd that is not open the fstat will fail. It will return -1 and set errno to EBADF. If it failed it will not touch the stat structure.

My man page says:
Code:
     The fstat() function will fail if:

     EBADF The fildes argument is not a valid open file  descrip-
           tor.

This User Gave Thanks to Perderabo For This Post:
homeboy
# 9  
Old 01-25-2011
Thanks so much Perderabo.
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