/* Open a stream to a file. Copyright (C) 2007-2023 Free Software Foundation, Inc. This file is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This file is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this program. If not, see <https://www.gnu.org/licenses/>. */ /* Written by Bruno Haible <bruno@clisp.org>, 2007. */ /* If the user's config.h happens to include <stdio.h>, let it include only the system's <stdio.h> here, so that orig_fopen doesn't recurse to rpl_fopen. */ #define _GL_ALREADY_INCLUDING_STDIO_H #include <config.h> /* Get the original definition of fopen. It might be defined as a macro. */ #include <stdio.h> #undef _GL_ALREADY_INCLUDING_STDIO_H static FILE * orig_fopen (const char *filename, const char *mode) { return fopen (filename, mode); } /* Specification. */ /* Write "stdio.h" here, not <stdio.h>, otherwise OSF/1 5.1 DTK cc eliminates this include because of the preliminary #include <stdio.h> above. */ #include "stdio.h" #include <errno.h> #include <fcntl.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> FILE * rpl_fopen (const char *filename, const char *mode) { int open_direction; int open_flags; #if GNULIB_FOPEN_GNU bool open_flags_gnu; # define BUF_SIZE 80 char fdopen_mode_buf[BUF_SIZE + 1]; #endif #if defined _WIN32 && ! defined __CYGWIN__ if (strcmp (filename, "/dev/null") == 0) filename = "NUL"; #endif /* Parse the mode. */ open_direction = 0; open_flags = 0; #if GNULIB_FOPEN_GNU open_flags_gnu = false; #endif { const char *p = mode; #if GNULIB_FOPEN_GNU char *q = fdopen_mode_buf; #endif for (; *p != '\0'; p++) { switch (*p) { case 'r': open_direction = O_RDONLY; #if GNULIB_FOPEN_GNU if (q < fdopen_mode_buf + BUF_SIZE) *q++ = *p; #endif continue; case 'w': open_direction = O_WRONLY; open_flags |= O_CREAT | O_TRUNC; #if GNULIB_FOPEN_GNU if (q < fdopen_mode_buf + BUF_SIZE) *q++ = *p; #endif continue; case 'a': open_direction = O_WRONLY; open_flags |= O_CREAT | O_APPEND; #if GNULIB_FOPEN_GNU if (q < fdopen_mode_buf + BUF_SIZE) *q++ = *p; #endif continue; case 'b': /* While it is non-standard, O_BINARY is guaranteed by gnulib <fcntl.h>. We can also assume that orig_fopen supports the 'b' flag. */ open_flags |= O_BINARY; #if GNULIB_FOPEN_GNU if (q < fdopen_mode_buf + BUF_SIZE) *q++ = *p; #endif continue; case '+': open_direction = O_RDWR; #if GNULIB_FOPEN_GNU if (q < fdopen_mode_buf + BUF_SIZE) *q++ = *p; #endif continue; #if GNULIB_FOPEN_GNU case 'x': open_flags |= O_EXCL; open_flags_gnu = true; continue; case 'e': open_flags |= O_CLOEXEC; open_flags_gnu = true; continue; #endif default: break; } #if GNULIB_FOPEN_GNU /* The rest of the mode string can be a platform-dependent extension. Copy it unmodified. */ { size_t len = strlen (p); if (len > fdopen_mode_buf + BUF_SIZE - q) len = fdopen_mode_buf + BUF_SIZE - q; memcpy (q, p, len); q += len; } #endif break; } #if GNULIB_FOPEN_GNU *q = '\0'; #endif } #if FOPEN_TRAILING_SLASH_BUG /* Fail if the mode requires write access and the filename ends in a slash, as POSIX says such a filename must name a directory <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>: "A pathname that contains at least one non-<slash> character and that ends with one or more trailing <slash> characters shall not be resolved successfully unless the last pathname component before the trailing <slash> characters names an existing directory" If the named file already exists as a directory, then if a mode that requires write access is specified, fopen() must fail because POSIX <https://pubs.opengroup.org/onlinepubs/9699919799/functions/fopen.html> says that it fails with errno = EISDIR in this case. If the named file does not exist or does not name a directory, then fopen() must fail since the file does not contain a '.' directory. */ { size_t len = strlen (filename); if (len > 0 && filename[len - 1] == '/') { int fd; struct stat statbuf; FILE *fp; if (open_direction != O_RDONLY) { errno = EISDIR; return NULL; } fd = open (filename, open_direction | open_flags, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH); if (fd < 0) return NULL; if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode)) { close (fd); errno = ENOTDIR; return NULL; } # if GNULIB_FOPEN_GNU fp = fdopen (fd, fdopen_mode_buf); # else fp = fdopen (fd, mode); # endif if (fp == NULL) { int saved_errno = errno; close (fd); errno = saved_errno; } return fp; } } #endif #if GNULIB_FOPEN_GNU if (open_flags_gnu) { int fd; FILE *fp; fd = open (filename, open_direction | open_flags, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH); if (fd < 0) return NULL; fp = fdopen (fd, fdopen_mode_buf); if (fp == NULL) { int saved_errno = errno; close (fd); errno = saved_errno; } return fp; } #endif return orig_fopen (filename, mode); }