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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><HTML><HEAD> <META NAME="GENERATOR" CONTENT="LinuxDoc-Tools 0.9.21"> <TITLE>libapr(apache portable runtime) programming tutorial: file-system directory handling</TITLE> <LINK HREF="apr-tutorial-8.html" REL=next> <LINK HREF="apr-tutorial-6.html" REL=previous> <LINK HREF="apr-tutorial.html#toc7" REL=contents></HEAD><BODY><A HREF="apr-tutorial-8.html">Next</A><A HREF="apr-tutorial-6.html">Previous</A><A HREF="apr-tutorial.html#toc7">Contents</A><HR><H2><A NAME="s7">7.</A> <A HREF="apr-tutorial.html#toc7">file-system directory handling</A></H2><P>When we handle file-system directories, we have to call apr_dir_open() at first. By apr_dir_open(), we have an apr_dir_t object. All we can do with apr_dir_t is to scan the directory. The API is apr_dir_read(). Finally, we call apr_dir_close() to close the directory. The prototype declarations are as follows:</P><P>/* excerpted from apr_file_info.h */<BLOCKQUOTE><CODE><PRE>APR_DECLARE(apr_status_t) apr_dir_open(apr_dir_t **new_dir, const char *dirname, apr_pool_t *pool);APR_DECLARE(apr_status_t) apr_dir_read(apr_finfo_t *finfo, apr_int32_t wanted, apr_dir_t *thedir);APR_DECLARE(apr_status_t) apr_dir_close(apr_dir_t *thedir);</PRE></CODE></BLOCKQUOTE></P><P>The first argument of apr_dir_open() is result argument. By which, we can get a newly created apr_dir_t object. The second argument is directory name. The third argument is memory pool to use.</P><P>The first argument of apr_dir_read() is result argument. As mentioned earlier, apr_finfo_t is complete type. Thus, we have to allocate its memory explicitly. apr_dir_read() returns an entry of the directory by apr_finfo_t. The entry is either file or directory. The second argument is bit-wised flag. The flags are defined in apr_file_info.h with APR_FINFO_ prefix, such as APR_FINFO_SIZE, APR_FINFO_TYPE and APR_FINFO_NAME. The third argument is apr_dir_t object to scan.</P><P>Here is a sample code: <BLOCKQUOTE><CODE><PRE>/* pseudo code about apr_dir_read() *//* no error checks */apr_pool_t *mp;apr_pool_create(&mp, NULL);const char *dirpath = "/home";/* directory path to scan */apr_dir_t *dir;apr_dir_open(&dir, dirpath, mp);/* create the apr_dir_t object */apr_finfo_t dirent;apr_dir_read(&dirent, APR_FINFO_DIRENT, dir);/* the apr_finfo_t object filled *//* dirent is the first entry of the directory. * the entry is either file or directory. */apr_dir_close(dir);</PRE></CODE></BLOCKQUOTE></P><P>In the sample code above we call apr_dir_read() only once, but we usually call apr_dir_read() multiple times to scan all files under the directory. To scan all files, we just keep calling apr_dir_read() while it returns APR_SUCCESS. Take a look at <A HREF="../sample/dir-sample.c">dir-sample.c</A> about precise usage.</P><P><BLOCKQUOTE><CODE><PRE>/* pseudo code about apr_dir_read() loop. error checks omitted *//* typical while loop of apr_dir_read() */apr_dir_open(&dir, dirpath, mp);while ((apr_dir_read(&dirent, APR_FINFO_NAME, dir)) == APR_SUCCESS) { printf("file name is %s\n", dirent.name);}apr_dir_close(dir);</PRE></CODE></BLOCKQUOTE></P><P>As you can imagine, apr_dir_t object has the current position. Calling apr_dir_read() makes the position move forward. We can rewind the (internal)position by apr_dir_rewind(). All the operations we can do with the position are just these two, moving forward and rewinding.</P><P>As you see in <A HREF="../sample/dir-sample.c">dir-sample.c</A>, if you scan directories recursively, you need to call apr_dir_open() recursively.</P><P><EM>REMARK</EM>: On Unix, apr_dir_read() returns apr_finfo_t object whose apr_file_t::fname is NULL</P><HR><A HREF="apr-tutorial-8.html">Next</A><A HREF="apr-tutorial-6.html">Previous</A><A HREF="apr-tutorial.html#toc7">Contents</A></BODY></HTML>⌨️ 快捷键说明
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