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Diffstat (limited to 'manual/filesys.texi')
| -rw-r--r-- | manual/filesys.texi | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/manual/filesys.texi b/manual/filesys.texi index e269663e70..31325268f9 100644 --- a/manual/filesys.texi +++ b/manual/filesys.texi @@ -327,6 +327,36 @@ conditions are defined for this function: @item EBADF The @var{dirstream} argument is not valid. @end table + +@code{readdir} is not thread safe. Multiple threads using +@code{readdir} on the same @var{dirstream} may overwrite the return +value. Use @code{readdir_r} when this is critical. +@end deftypefun + +@comment dirent.h +@comment GNU +@deftypefun int readdir_r (DIR *@var{dirstream}, struct *@var{entry}, struct **@var{result}) +This function is the reentrant version of @code{reentrant}. Like +@code{readdir} it returns the next entry from the directory. But to +prevent conflicts for simultanously running threads the result is not +stored in some internal memory. Instead the argument @var{entry} has to +point to a place where the result is stored. + +The return value is @code{0} in case the next entry was read +successfully. In this case a pointer to the result is returned in +*@var{result}. It is not required that *@var{result} is the same as +@var{entry}. If somethings goes wrong while exeucting @code{readdir_r} +the function return @code{-1}. The @code{errno} variable is set like +described for @code{readdir}. + +@strong{Portability Note:} On some systems, @code{readdir_r} may not +return a terminated string as the file name even if no @code{d_reclen} +element is available in @code{struct dirent} and the file name as the +maximal allowed size. Modern systems all have the @code{d_reclen} field +and on old systems multi threading is not critical. In any case, there +is no such problem with the @code{readdir} function so that even on +systems without @code{d_reclen} field one could use multiple threads by +using external locking. @end deftypefun @comment dirent.h |