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1449
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1 /*
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2 * Public domain dup2() lookalike
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3 * by Curtis Jackson @ AT&T Technologies, Burlington, NC
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4 * electronic address: burl!rcj
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5 *
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6 * dup2 performs the following functions:
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7 *
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8 * Check to make sure that fd1 is a valid open file descriptor.
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9 * Check to see if fd2 is already open; if so, close it.
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10 * Duplicate fd1 onto fd2; checking to make sure fd2 is a valid fd.
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11 * Return fd2 if all went well; return BADEXIT otherwise.
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12 */
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13
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14 #include <fcntl.h>
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15
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16 #define BADEXIT -1
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17
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18 int
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19 dup2(fd1, fd2)
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20 int fd1, fd2;
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21 {
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22 if (fd1 != fd2) {
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23 if (fcntl(fd1, F_GETFL) < 0)
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24 return BADEXIT;
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25 if (fcntl(fd2, F_GETFL) >= 0)
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26 close(fd2);
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27 if (fcntl(fd1, F_DUPFD, fd2) < 0)
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28 return BADEXIT;
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29 }
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30 return fd2;
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31 }
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