20 <<freopen>>---open a file using an existing file descriptor
29 	FILE *freopen(const char *restrict <[file]>, const char *restrict <[mode]>,
30 		      FILE *restrict <[fp]>);
31 	FILE *freopen( const char *restrict <[file]>,
32 		      const char *restrict <[mode]>, FILE *restrict <[fp]>);
35 Use this variant of <<fopen>> if you wish to specify a particular file
37 the file.
39 If <[fp]> was associated with another file or stream, <<freopen>>
40 closes that other file or stream (but ignores any errors while closing
43 <[file]> and <[mode]> are used just as in <<fopen>>.
45 If <[file]> is <<NULL>>, the underlying stream is modified rather than
46 closed.  The file cannot be given a more permissive access mode (for
47 example, a <[mode]> of "w" will fail on a read-only file descriptor),
53 file cannot be opened as specified, the result is <<NULL>>.
73  * Re-direct an existing, open (probably) file to some other file.
76 FILE *
78        const char *__restrict file,  in freopen()  argument
80        register FILE *__restrict fp)  in freopen()
111    * which file descriptor (if any) was associated with it.  in freopen()
114    * This is unnecessary if it was not a Unix file.  in freopen()
125        * If file is NULL, the file should not be closed.  in freopen()
127       if (fp->_close != NULL && file != NULL)  in freopen()
132    * Now get a new descriptor to refer to the new file, or reuse the  in freopen()
133    * existing file descriptor if file is NULL.  in freopen()
136   if (file != NULL)  in freopen()
138       f = open ((char *) file, oflags, 0666);  in freopen()
146        * Reuse the file descriptor, but only if the new access mode is  in freopen()