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| <h3 class="section">29.11 Identifying Who Logged In</h3> |
| |
| <p><a name="index-login-name_002c-determining-3329"></a><a name="index-user-ID_002c-determining-3330"></a> |
| You can use the functions listed in this section to determine the login |
| name of the user who is running a process, and the name of the user who |
| logged in the current session. See also the function <code>getuid</code> and |
| friends (see <a href="Reading-Persona.html#Reading-Persona">Reading Persona</a>). How this information is collected by |
| the system and how to control/add/remove information from the background |
| storage is described in <a href="User-Accounting-Database.html#User-Accounting-Database">User Accounting Database</a>. |
| |
| <p>The <code>getlogin</code> function is declared in <samp><span class="file">unistd.h</span></samp>, while |
| <code>cuserid</code> and <code>L_cuserid</code> are declared in <samp><span class="file">stdio.h</span></samp>. |
| <a name="index-stdio_002eh-3331"></a><a name="index-unistd_002eh-3332"></a> |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| |
| <div class="defun"> |
| — Function: char * <b>getlogin</b> (<var>void</var>)<var><a name="index-getlogin-3333"></a></var><br> |
| <blockquote><p>The <code>getlogin</code> function returns a pointer to a string containing the |
| name of the user logged in on the controlling terminal of the process, |
| or a null pointer if this information cannot be determined. The string |
| is statically allocated and might be overwritten on subsequent calls to |
| this function or to <code>cuserid</code>. |
| </p></blockquote></div> |
| |
| <!-- stdio.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: char * <b>cuserid</b> (<var>char *string</var>)<var><a name="index-cuserid-3334"></a></var><br> |
| <blockquote><p>The <code>cuserid</code> function returns a pointer to a string containing a |
| user name associated with the effective ID of the process. If |
| <var>string</var> is not a null pointer, it should be an array that can hold |
| at least <code>L_cuserid</code> characters; the string is returned in this |
| array. Otherwise, a pointer to a string in a static area is returned. |
| This string is statically allocated and might be overwritten on |
| subsequent calls to this function or to <code>getlogin</code>. |
| |
| <p>The use of this function is deprecated since it is marked to be |
| withdrawn in XPG4.2 and has already been removed from newer revisions of |
| POSIX.1. |
| </p></blockquote></div> |
| |
| <!-- stdio.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Macro: int <b>L_cuserid</b><var><a name="index-L_005fcuserid-3335"></a></var><br> |
| <blockquote><p>An integer constant that indicates how long an array you might need to |
| store a user name. |
| </p></blockquote></div> |
| |
| <p>These functions let your program identify positively the user who is |
| running or the user who logged in this session. (These can differ when |
| setuid programs are involved; see <a href="Process-Persona.html#Process-Persona">Process Persona</a>.) The user cannot |
| do anything to fool these functions. |
| |
| <p>For most purposes, it is more useful to use the environment variable |
| <code>LOGNAME</code> to find out who the user is. This is more flexible |
| precisely because the user can set <code>LOGNAME</code> arbitrarily. |
| See <a href="Standard-Environment.html#Standard-Environment">Standard Environment</a>. |
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