Mercurial > gnulib
view doc/posix-functions/unlinkat.texi @ 40131:9c7eed94d112
unlinkat: Fix compilation error on Android 4.3.
* lib/unistd.in.h: Include <fcntl.h> when module 'unlinkat' is in use
also on Android.
* doc/posix-functions/unlinkat.texi: Mention the issue.
author | Bruno Haible <bruno@clisp.org> |
---|---|
date | Fri, 25 Jan 2019 00:08:52 +0100 |
parents | 65bc0f9b42bf |
children |
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@node unlinkat @section @code{unlinkat} @findex unlinkat POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/unlinkat.html} Gnulib module: unlinkat Portability problems fixed by Gnulib: @itemize @item This function is missing on some platforms: glibc 2.3.6, Mac OS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Cygwin 1.5.x, mingw, MSVC 14, Interix 3.5, BeOS. But the replacement function is not safe to be used in libraries and is not multithread-safe. @item This function is declared in @code{<fcntl.h>}, not in @code{<unistd.h>}, on some platforms: Cygwin 1.7.1, Android 4.3. @item On Mac OS X 10.10, in a writable HFS mount, @code{unlinkat(fd, "..", 0)} succeeds without doing anything. @item Some systems mistakenly succeed on @code{unlinkat(fd,"file/",flag)}: GNU/Hurd, Solaris 9. @end itemize Portability problems not fixed by Gnulib: @itemize @item When @code{unlinkat(fd,name,AT_REMOVEDIR)} fails because the specified directory is not empty, the @code{errno} value is system dependent. @item POSIX requires that @code{unlinkdir(fd,"link-to-empty/",AT_REMOVEDIR)} remove @file{empty} and leave @file{link-to-empty} as a dangling symlink. This is counter-intuitive, so some systems fail with @code{ENOTDIR} instead: glibc @item Some systems allow a superuser to unlink directories, even though this can cause file system corruption. The error given if a process is not permitted to unlink directories varies across implementations; it is not always the POSIX value of @code{EPERM}. Meanwhile, if a process has the ability to unlink directories, POSIX requires that @code{unlinkat(fd,"symlink-to-dir/",0)} remove @file{dir} and leave @file{symlink-to-dir} dangling; this behavior is counter-intuitive. The gnulib module @code{unlinkdir} can help determine whether code must be cautious of unlinking directories. @item Removing an open file is non-portable: On Unix this allows the programs that have the file already open to continue working with it; the file's storage is only freed when the no process has the file open any more. On Windows, the attempt to remove an open file fails. @end itemize