1 /*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Chris Torek. 7 * 8 * %sccs.include.redist.c% 9 */ 10 11 #if defined(LIBC_SCCS) && !defined(lint) 12 static char sccsid[] = "@(#)freopen.c 5.6 (Berkeley) 02/24/91"; 13 #endif /* LIBC_SCCS and not lint */ 14 15 #include <sys/types.h> 16 #include <sys/stat.h> 17 #include <fcntl.h> 18 #include <errno.h> 19 #include <unistd.h> 20 #include <stdio.h> 21 #include <stdlib.h> 22 #include "local.h" 23 24 /* 25 * Re-direct an existing, open (probably) file to some other file. 26 * ANSI is written such that the original file gets closed if at 27 * all possible, no matter what. 28 */ 29 FILE * 30 freopen(file, mode, fp) 31 const char *file, *mode; 32 register FILE *fp; 33 { 34 register int f; 35 int flags, isopen, oflags, sverrno, wantfd; 36 37 if ((flags = __sflags(mode, &oflags)) == 0) { 38 (void) fclose(fp); 39 return (NULL); 40 } 41 42 if (!__sdidinit) 43 __sinit(); 44 45 /* 46 * There are actually programs that depend on being able to "freopen" 47 * descriptors that weren't originally open. Keep this from breaking. 48 * Remember whether the stream was open to begin with, and which file 49 * descriptor (if any) was associated with it. If it was attached to 50 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 51 * should work. This is unnecessary if it was not a Unix file. 52 */ 53 if (fp->_flags == 0) { 54 fp->_flags = __SEOF; /* hold on to it */ 55 isopen = 0; 56 wantfd = -1; 57 } else { 58 /* flush the stream; ANSI doesn't require this. */ 59 if (fp->_flags & __SWR) 60 (void) __sflush(fp); 61 /* if close is NULL, closing is a no-op, hence pointless */ 62 isopen = fp->_close != NULL; 63 if ((wantfd = fp->_file) < 0 && isopen) { 64 (void) (*fp->_close)(fp->_cookie); 65 isopen = 0; 66 } 67 } 68 69 /* Get a new descriptor to refer to the new file. */ 70 f = open(file, oflags, DEFFILEMODE); 71 if (f < 0 && isopen) { 72 /* If out of fd's close the old one and try again. */ 73 if (errno == ENFILE || errno == EMFILE) { 74 (void) (*fp->_close)(fp->_cookie); 75 isopen = 0; 76 f = open(file, oflags, DEFFILEMODE); 77 } 78 } 79 sverrno = errno; 80 81 /* 82 * Finish closing fp. Even if the open succeeded above, we cannot 83 * keep fp->_base: it may be the wrong size. This loses the effect 84 * of any setbuffer calls, but stdio has always done this before. 85 */ 86 if (isopen) 87 (void) (*fp->_close)(fp->_cookie); 88 if (fp->_flags & __SMBF) 89 free((char *)fp->_bf._base); 90 fp->_w = 0; 91 fp->_r = 0; 92 fp->_p = NULL; 93 fp->_bf._base = NULL; 94 fp->_bf._size = 0; 95 fp->_lbfsize = 0; 96 if (HASUB(fp)) 97 FREEUB(fp); 98 fp->_ub._size = 0; 99 if (HASLB(fp)) 100 FREELB(fp); 101 fp->_lb._size = 0; 102 103 if (f < 0) { /* did not get it after all */ 104 fp->_flags = 0; /* set it free */ 105 errno = sverrno; /* restore in case _close clobbered */ 106 return (NULL); 107 } 108 109 /* 110 * If reopening something that was open before on a real file, try 111 * to maintain the descriptor. Various C library routines (perror) 112 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 113 */ 114 if (wantfd >= 0 && f != wantfd) { 115 if (dup2(f, wantfd) >= 0) { 116 (void) close(f); 117 f = wantfd; 118 } 119 } 120 121 fp->_flags = flags; 122 fp->_file = f; 123 fp->_cookie = fp; 124 fp->_read = __sread; 125 fp->_write = __swrite; 126 fp->_seek = __sseek; 127 fp->_close = __sclose; 128 return (fp); 129 } 130