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* doc/posix-functions/stat.texi (stat): * doc/posix-functions/lstat.texi (lstat): * doc/posix-functions/fstatat.texi (fstatat): * doc/posix-functions/fstat.texi (fstat): Move general 'struct stat' stuff to sys_stat.texi, leaving behind a pointer. * doc/posix-headers/sys_stat.texi (sys/stat.h): Merge duplicate info about 'struct stat' problems into here. Mention issues with OpenVMS, GNU/Linux NFS, NetApp, ClearCase, and suggest partial workarounds.
76 lines
2.7 KiB
Plaintext
76 lines
2.7 KiB
Plaintext
@node sys/stat.h
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@section @file{sys/stat.h}
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POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/basedefs/sys_stat.h.html}
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Gnulib module: sys_stat
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Portability problems fixed by Gnulib:
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@itemize
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@item
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The type @code{mode_t} is not defined on some platforms:
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MSVC 9.
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@item
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Some macros, such as @code{S_IFMT} or @code{S_IFIFO}, are missing on some
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platforms.
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@item
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The macros @code{S_ISBLK}, @code{S_ISCHR}, @code{S_ISDIR}, @code{S_ISFIFO},
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@code{S_ISLNK}, @code{S_ISREG}, @code{S_ISSOCK} are broken on some platforms.
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@item
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Some platforms define macros, such as @code{S_ISDOOR}, that are not defined
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on other platforms.
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@item
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The functions @code{lstat} and @code{mkdir} are not declared on some platforms:
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mingw, MSVC 9.
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@item
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The macros @code{UTIME_NOW} and @code{UTIME_OMIT} are missing on some
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platforms.
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@item
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On some platforms, @code{struct stat} does not include @code{st_atim},
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@code{st_mtim}, or @code{st_ctim} members. Use the gnulib module
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@samp{stat-time} for accessors to portably get at subsecond resolution.
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@end itemize
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Portability problems not fixed by Gnulib:
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@itemize
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@item
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The macro @code{S_IFBLK} is missing on some platforms:
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MSVC 9.
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@item
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On Windows platforms (excluding Cygwin), @code{st_ino} is always 0.
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@item
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On OpenVMS, @code{st_ino} is an array of three @code{ino_t} values,
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not a single value.
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@item
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To partially work around the previous two problems, you can test for
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nonzero @code{st_ino} and use the Gnulib @code{same-inode} module to
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compare nonzero values. For example, @code{(a.st_ino && SAME_INODE
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(a, b))} is true if the @code{struct stat} values @code{a} and
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@code{b} are known to represent the same file, @code{(a.st_ino &&
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!SAME_INODE (a, b))} is true if they are known to represent different
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files, and @code{!a.st_ino} is true if it is not known whether they
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represent different files.
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@item
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On some platforms, two different files may have the same @code{st_dev}
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and @code{st_ino} values, even when @code{st_ino} is nonzero:
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@itemize
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@item
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GNU/Linux NFS servers that export all local file systems as a single
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NFS file system, if a local @code{st_dev} exceeds 255, or if a local
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@code{st_ino} exceeds 16777215.
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@item
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Network Appliance NFS servers in snapshot directories; see Network
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Appliance bug #195.
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@item
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ClearCase MVFS; see bug id ATRia04618.
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@end itemize
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One partial workaround is to compare other file metadata such as
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@code{st_mode} and @code{st_mtime} to detect this bug, but this
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approach does not work on files whose metadata are being changed by
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other programs.
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@item
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On some file systems, @code{st_size} contains bogus information for
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symlinks; use the Gnulib module @code{areadlink-with-size} for a
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better way to get symlink contents.
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@end itemize
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