[Bug-gnulib] addition: copy-file.h, copy-file.c

[Bruno Haible]

Hi,

I hope it's not getting boring. Here is a module to copy a regular
file. No bells and whistles; only the modification time is copied too.

The need for this function arises when making backup files. We have a
module 'backupfile' which goes to all lengths to determine the name of
a backup file; so it appears legitimate to add the function for
actually creating the backup file.

Besides the use in GNU gettext, this function should also be useful in
GNU tar when making copies of files on systems that don't support hard
links (a bug report I sent on 2003-01-13).

The code is loosely based on the buffering technique seen in fileutils.

Bruno


=========================== copy-file.h ===========================
/* Copying of files.
   Copyright (C) 2001-2002 Free Software Foundation, Inc.
   Written by Bruno Haible <address@hidden>, 2001.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Copy a regular file: from src_filename to dest_filename.
   The destination file is assumed to be a backup file.
   Exit upon failure.  */
extern void copy_file (const char *src_filename, const char *dest_filename);
=========================== copy-file.c ===========================
/* Copying of files.
   Copyright (C) 2001-2002 Free Software Foundation, Inc.
   Written by Bruno Haible <address@hidden>, 2001.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */


#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

/* Specification.  */
#include "copy-file.h"

#include <errno.h>
#include <fcntl.h>
#include <sys/stat.h>

#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif

#if HAVE_UTIME || HAVE_UTIMES
# if HAVE_UTIME_H
#  include <utime.h>
# else
#  include <sys/utime.h>
# endif
#endif

#include "error.h"
#include "full-write.h"
#include "binary-io.h"
#include "exit.h"
#include "gettext.h"

#define _(str) gettext (str)

void
copy_file (const char *src_filename, const char *dest_filename)
{
  int src_fd;
  struct stat statbuf;
  int mode;
  int dest_fd;
  char buf[4096];
  const int buf_size = sizeof (buf);

  src_fd = open (src_filename, O_RDONLY | O_BINARY);
  if (src_fd < 0 || fstat (src_fd, &statbuf) < 0)
    error (EXIT_FAILURE, errno, _("error while opening \"%s\" for reading"),
           src_filename);

  mode = statbuf.st_mode & 07777;

  dest_fd = open (dest_filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0600);
  if (dest_fd < 0)
    error (EXIT_FAILURE, errno, _("cannot open backup file \"%s\" for writing"),
           dest_filename);

  /* Copy the file contents.  */
  for (;;)
    {
      ssize_t n_read = read (src_fd, buf, buf_size);
      if (n_read < 0)
        {
#ifdef EINTR
          if (errno == EINTR)
            continue;
#endif
          error (EXIT_FAILURE, errno, _("error reading \"%s\""), src_filename);
        }
      if (n_read == 0)
        break;

      if (full_write (dest_fd, buf, n_read) < n_read)
        error (EXIT_FAILURE, errno, _("error writing \"%s\""), dest_filename);
    }

  if (close (dest_fd) < 0)
    error (EXIT_FAILURE, errno, _("error writing \"%s\""), dest_filename);
  if (close (src_fd) < 0)
    error (EXIT_FAILURE, errno, _("error after reading \"%s\""), src_filename);

  /* Preserve the access and modification times.  */
#if HAVE_UTIME
  {
    struct utimbuf ut;

    ut.actime = statbuf.st_atime;
    ut.modtime = statbuf.st_mtime;
    utime (dest_filename, &ut);
  }
#elif HAVE_UTIMES
  {
    struct timeval ut[2];

    ut[0].tv_sec = statbuf.st_atime; ut[0].tv_usec = 0;
    ut[1].tv_sec = statbuf.st_mtime; ut[1].tv_usec = 0;
    utimes (dest_filename, &ut);
  }
#endif

  /* Preserve the access permissions.  */
  chmod (dest_filename, mode);
}