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31 lines
685 B
31 lines
685 B
4 years ago
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/*
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* Public domain dup2() lookalike
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* by Curtis Jackson @ AT&T Technologies, Burlington, NC
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* electronic address: burl!rcj
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*
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* dup2 performs the following functions:
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*
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* Check to make sure that fd1 is a valid open file descriptor.
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* Check to see if fd2 is already open; if so, close it.
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* Duplicate fd1 onto fd2; checking to make sure fd2 is a valid fd.
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* Return fd2 if all went well; return BADEXIT otherwise.
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*/
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#include <fcntl.h>
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#define BADEXIT -1
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int
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dup2(int fd1, int fd2)
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{
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if (fd1 != fd2) {
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if (fcntl(fd1, F_GETFL) < 0)
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return BADEXIT;
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if (fcntl(fd2, F_GETFL) >= 0)
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close(fd2);
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if (fcntl(fd1, F_DUPFD, fd2) < 0)
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return BADEXIT;
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}
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return fd2;
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}
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