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| <h4 class="subsection">29.13.3 Scanning the List of All Users</h4> |
| |
| <p><a name="index-scanning-the-user-list-3399"></a> |
| This section explains how a program can read the list of all users in |
| the system, one user at a time. The functions described here are |
| declared in <samp><span class="file">pwd.h</span></samp>. |
| |
| <p>You can use the <code>fgetpwent</code> function to read user entries from a |
| particular file. |
| |
| <!-- pwd.h --> |
| <!-- SVID --> |
| <div class="defun"> |
| — Function: struct passwd * <b>fgetpwent</b> (<var>FILE *stream</var>)<var><a name="index-fgetpwent-3400"></a></var><br> |
| <blockquote><p>This function reads the next user entry from <var>stream</var> and returns a |
| pointer to the entry. The structure is statically allocated and is |
| rewritten on subsequent calls to <code>fgetpwent</code>. You must copy the |
| contents of the structure if you wish to save the information. |
| |
| <p>The stream must correspond to a file in the same format as the standard |
| password database file. |
| </p></blockquote></div> |
| |
| <!-- pwd.h --> |
| <!-- GNU --> |
| <div class="defun"> |
| — Function: int <b>fgetpwent_r</b> (<var>FILE *stream, struct passwd *result_buf, char *buffer, size_t buflen, struct passwd **result</var>)<var><a name="index-fgetpwent_005fr-3401"></a></var><br> |
| <blockquote><p>This function is similar to <code>fgetpwent</code> in that it reads the next |
| user entry from <var>stream</var>. But the result is returned in the |
| structure pointed to by <var>result_buf</var>. The |
| first <var>buflen</var> bytes of the additional buffer pointed to by |
| <var>buffer</var> are used to contain additional information, normally |
| strings which are pointed to by the elements of the result structure. |
| |
| <p>The stream must correspond to a file in the same format as the standard |
| password database file. |
| |
| <p>If the function returns zero <var>result</var> points to the structure with |
| the wanted data (normally this is in <var>result_buf</var>). If errors |
| occurred the return value is nonzero and <var>result</var> contains a null |
| pointer. |
| </p></blockquote></div> |
| |
| <p>The way to scan all the entries in the user database is with |
| <code>setpwent</code>, <code>getpwent</code>, and <code>endpwent</code>. |
| |
| <!-- pwd.h --> |
| <!-- SVID, BSD --> |
| <div class="defun"> |
| — Function: void <b>setpwent</b> (<var>void</var>)<var><a name="index-setpwent-3402"></a></var><br> |
| <blockquote><p>This function initializes a stream which <code>getpwent</code> and |
| <code>getpwent_r</code> use to read the user database. |
| </p></blockquote></div> |
| |
| <!-- pwd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: struct passwd * <b>getpwent</b> (<var>void</var>)<var><a name="index-getpwent-3403"></a></var><br> |
| <blockquote><p>The <code>getpwent</code> function reads the next entry from the stream |
| initialized by <code>setpwent</code>. It returns a pointer to the entry. The |
| structure is statically allocated and is rewritten on subsequent calls |
| to <code>getpwent</code>. You must copy the contents of the structure if you |
| wish to save the information. |
| |
| <p>A null pointer is returned when no more entries are available. |
| </p></blockquote></div> |
| |
| <!-- pwd.h --> |
| <!-- GNU --> |
| <div class="defun"> |
| — Function: int <b>getpwent_r</b> (<var>struct passwd *result_buf, char *buffer, int buflen, struct passwd **result</var>)<var><a name="index-getpwent_005fr-3404"></a></var><br> |
| <blockquote><p>This function is similar to <code>getpwent</code> in that it returns the next |
| entry from the stream initialized by <code>setpwent</code>. Like |
| <code>fgetpwent_r</code>, it uses the user-supplied buffers in |
| <var>result_buf</var> and <var>buffer</var> to return the information requested. |
| |
| <p>The return values are the same as for <code>fgetpwent_r</code>. |
| |
| </blockquote></div> |
| |
| <!-- pwd.h --> |
| <!-- SVID, BSD --> |
| <div class="defun"> |
| — Function: void <b>endpwent</b> (<var>void</var>)<var><a name="index-endpwent-3405"></a></var><br> |
| <blockquote><p>This function closes the internal stream used by <code>getpwent</code> or |
| <code>getpwent_r</code>. |
| </p></blockquote></div> |
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