Originální popis anglicky:
getlogin, getlogin_r - get login name
Návod, kniha: POSIX Programmer's Manual
#include <unistd.h>
char *getlogin(void);
int getlogin_r(char *name, size_t namesize);
The
getlogin() function shall return a pointer to a string containing the
user name associated by the login activity with the controlling terminal of
the current process. If
getlogin() returns a non-null pointer, then
that pointer points to the name that the user logged in under, even if there
are several login names with the same user ID.
The
getlogin() function need not be reentrant. A function that is not
required to be reentrant is not required to be thread-safe.
The
getlogin_r() function shall put the name associated by the login
activity with the controlling terminal of the current process in the character
array pointed to by
name. The array is
namesize characters long
and should have space for the name and the terminating null character. The
maximum size of the login name is {LOGIN_NAME_MAX}.
If
getlogin_r() is successful,
name points to the name the user
used at login, even if there are several login names with the same user ID.
Upon successful completion,
getlogin() shall return a pointer to the
login name or a null pointer if the user's login name cannot be found.
Otherwise, it shall return a null pointer and set
errno to indicate the
error.
The return value from
getlogin() may point to static data whose content
is overwritten by each call.
If successful, the
getlogin_r() function shall return zero; otherwise, an
error number shall be returned to indicate the error.
The
getlogin() and
getlogin_r() functions may fail if:
- EMFILE
- {OPEN_MAX} file descriptors are currently open in the
calling process.
- ENFILE
- The maximum allowable number of files is currently open in
the system.
- ENXIO
- The calling process has no controlling terminal.
The
getlogin_r() function may fail if:
- ERANGE
- The value of namesize is smaller than the length of
the string to be returned including the terminating null character.
The following sections are informative.
The following example calls the
getlogin() function to obtain the name of
the user associated with the calling process, and passes this information to
the
getpwnam() function to get the associated user database
information.
#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>
#include <stdio.h>
...
char *lgn;
struct passwd *pw;
...
if ((lgn = getlogin()) == NULL || (pw = getpwnam(lgn)) == NULL) {
fprintf(stderr, "Get of user information failed.\n"); exit(1);
}
Three names associated with the current process can be determined:
getpwuid(
geteuid()) shall return the name associated with the
effective user ID of the process;
getlogin() shall return the name
associated with the current login activity; and
getpwuid(
getuid()) shall return the name associated with the real user ID of the
process.
The
getlogin_r() function is thread-safe and returns values in a
user-supplied buffer instead of possibly using a static data area that may be
overwritten by each call.
The
getlogin() function returns a pointer to the user's login name. The
same user ID may be shared by several login names. If it is desired to get the
user database entry that is used during login, the result of
getlogin()
should be used to provide the argument to the
getpwnam() function.
(This might be used to determine the user's login shell, particularly where a
single user has multiple login shells with distinct login names, but the same
user ID.)
The information provided by the
cuserid() function, which was originally
defined in the POSIX.1-1988 standard and subsequently removed, can be obtained
by the following:
while the information provided by historical implementations of
cuserid()
can be obtained by:
The thread-safe version of this function places the user name in a user-supplied
buffer and returns a non-zero value if it fails. The non-thread-safe version
may return the name in a static data area that may be overwritten by each
call.
None.
getpwnam() ,
getpwuid() ,
geteuid() ,
getuid() , the
Base Definitions volume of IEEE Std 1003.1-2001,
<limits.h>,
<unistd.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
