stdio-common/tmpfile.c

   1 /* Open a stdio stream on an anonymous temporary file.  Generic/POSIX version.
   2    Copyright (C) 1991-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <fcntl.h>
  20 #include <stdio.h>
  21 #include <unistd.h>
  22
  23 #include <iolibio.h>
  24 #define __fdopen _IO_fdopen
  25 #ifndef tmpfile
  26 # define tmpfile __new_tmpfile
  27 #endif
  28
  29
  30 /* This returns a new stream opened on a temporary file (generated
  31    by tmpnam).  The file is opened with mode "w+b" (binary read/write).
  32    If we couldn't generate a unique filename or the file couldn't
  33    be opened, NULL is returned.  */
  34 FILE *
  35 tmpfile (void)
  36 {
  37   int fd;
  38   FILE *f;
  39   int flags = 0;
  40 #ifdef FLAGS
  41   flags = FLAGS;
  42 #endif
  43
  44   /* First try a system specific method.  */
  45   fd = __gen_tempfd (flags);
  46
  47   if (fd < 0)
  48     {
  49       char buf[FILENAME_MAX];
  50
  51       if (__path_search (buf, sizeof buf, NULL, "tmpf", 0))
  52         return NULL;
  53
  54       fd = __gen_tempname (buf, 0, flags, __GT_FILE);
  55       if (fd < 0)
  56         return NULL;
  57
  58       /* Note that this relies on the Unix semantics that
  59          a file is not really removed until it is closed.  */
  60       (void) __unlink (buf);
  61     }
  62
  63   if ((f = __fdopen (fd, "w+b")) == NULL)
  64     __close (fd);
  65
  66   return f;
  67 }
  68
  69 #if !defined O_LARGEFILE || O_LARGEFILE == 0
  70 weak_alias (__new_tmpfile, tmpfile64)
  71 #endif
  72
  73 #ifndef FLAGS /* Not for tmpfile64.  */
  74 # undef tmpfile
  75 # include <shlib-compat.h>
  76 versioned_symbol (libc, __new_tmpfile, tmpfile, GLIBC_2_1);
  77 #endif