Tribblix: manual page: getutxent.3c

GETUTXENT(3C) Standard C Library Functions GETUTXENT(3C)

NAME

getutxent, getutxid, getutxline, pututxline, setutxent, endutxent,
utmpxname, getutmp, getutmpx, updwtmp, updwtmpx - user accounting
database functions

SYNOPSIS

#include <utmpx.h>

struct utmpx *getutxent(void);

struct utmpx *getutxid(const struct utmpx *id);

struct utmpx *getutxline(const struct utmpx *line);

struct utmpx *pututxline(const struct utmpx *utmpx);

void setutxent(void);

void endutxent(void);

int utmpxname(const char *file);

void getutmp(struct utmpx *utmpx, struct utmp *utmp);

void getutmpx(struct utmp *utmp, struct utmpx *utmpx);

void updwtmp(char *wfile, struct utmp *utmp);

void updwtmpx(char *wfilex, struct utmpx *utmpx);

DESCRIPTION

These functions provide access to the user accounting database, utmpx
(see utmpx(5)). Entries in the database are described by the
definitions and data structures in <utmpx.h>.

The utmpx structure contains the following members:

char ut_user[32]; /* user login name */
char ut_id[4]; /* /etc/inittab id */
/* (usually line #) */
char ut_line[32]; /* device name */
/* (console, lnxx) */
pid_t ut_pid; /* process id */
short ut_type; /* type of entry */
struct exit_status ut_exit; /* exit status of a process */
/* marked as DEAD_PROCESS */
struct timeval ut_tv; /* time entry was made */
int ut_session; /* session ID, used for */
/* windowing */
short ut_syslen; /* significant length of */
/* ut_host */
/* including terminating null */
char ut_host[257]; /* host name, if remote */

The exit_status structure includes the following members:

short e_termination; /* termination status */
short e_exit; /* exit status */

getutxent()
The getutxent() function reads in the next entry from a utmpx
database. If the database is not already open, it opens it. If it
reaches the end of the database, it fails.

getutxid()
The getutxid() function searches forward from the current point in
the utmpx database until it finds an entry with a ut_type matching
id->ut_type, if the type specified is RUN_LVL, BOOT_TIME, DOWN_TIME,
OLD_TIME, or NEW_TIME. If the type specified in id is INIT_PROCESS,
LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS, then getutxid() will
return a pointer to the first entry whose type is one of these four
and whose ut_id member matches id->ut_id. If the end of database is
reached without a match, it fails.

getutxline()
The getutxline() function searches forward from the current point in
the utmpx database until it finds an entry of the type LOGIN_PROCESS
or USER_PROCESS which also has a ut_line string matching the
line->ut_line string. If the end of the database is reached without
a match, it fails.

pututxline()
The pututxline() function writes the supplied utmpx structure into
the utmpx database. It uses getutxid() to search forward for the
proper place if it finds that it is not already at the proper place.
It is expected that normally the user of pututxline() will have
searched for the proper entry using one of the getutx() routines. If
so, pututxline() will not search. If pututxline() does not find a
matching slot for the new entry, it will add a new entry to the end
of the database. It returns a pointer to the utmpx structure. When
called by a non-root user, pututxline() invokes a setuid() root
program to verify and write the entry, since the utmpx database is
normally writable only by root. In this event, the ut_name member
must correspond to the actual user name associated with the process;
the ut_type member must be either USER_PROCESS or DEAD_PROCESS; and
the ut_line member must be a device special file and be writable by
the user.

setutxent()
The setutxent() function resets the input stream to the beginning.
This should be done before each search for a new entry if it is
desired that the entire database be examined.

endutxent()
The endutxent() function closes the currently open database.

utmpxname()
The utmpxname() function allows the user to change the name of the
database file examined from /var/adm/utmpx to any other file, most
often /var/adm/wtmpx. If the file does not exist, this will not be
apparent until the first attempt to reference the file is made. The
utmpxname() function does not open the file, but closes the old file
if it is currently open and saves the new file name. The new file
name must end with the "x" character to allow the name of the
corresponding utmp file to be easily obtainable.; otherwise, an error
value of 0 is returned. The function returns 1 on success.

getutmp()
The getutmp() function copies the information stored in the members
of the utmpx structure to the corresponding members of the utmp
structure. If the information in any member of utmpx does not fit in
the corresponding utmp member, the data is silently truncated. (See
getutent(3C) for utmp structure)

getutmpx()
The getutmpx() function copies the information stored in the members
of the utmp structure to the corresponding members of the utmpx
structure. (See getutent(3C) for utmp structure)

updwtmp()
The updwtmp() function can be used in two ways.

If wfile is /var/adm/wtmp, the utmp format record supplied by the
caller is converted to a utmpx format record and the /var/adm/wtmpx
file is updated (because the /var/adm/wtmp file no longer exists,
operations on wtmp are converted to operations on wtmpx by the
library functions.

If wfile is a file other than /var/adm/wtmp, it is assumed to be an
old file in utmp format and is updated directly with the utmp format
record supplied by the caller.

updwtmpx()
The updwtmpx() function writes the contents of the utmpx structure
pointed to by utmpx to the database.

utmpx structure
The values of the e_termination and e_exit members of the ut_exit
structure are valid only for records of type DEAD_PROCESS. For utmpx
entries created by init(8), these values are set according to the
result of the wait() call that init performs on the process when the
process exits. See the wait(3C), manual page for the values init
uses. Applications creating utmpx entries can set ut_exit values
using the following code example:

u->ut_exit.e_termination = WTERMSIG(process->p_exit)
u->ut_exit.e_exit = WEXITSTATUS(process->p_exit)

See wait.h(3HEAD) for descriptions of the WTERMSIG and WEXITSTATUS
macros.

The ut_session member is not acted upon by the operating system. It
is used by applications interested in creating utmpx entries.

For records of type USER_PROCESS, the nonuserx() macro uses value of
the ut_exit.e_exit member to mark utmpx entries as real logins (as
opposed to multiple xterms started by the same user on a window
system). This allows the system utilities that display users to
obtain an accurate indication of the number of actual users, while
still permitting each pty to have a utmpx record (as most
applications expect). The NONROOT_USRX macro defines the value that
login places in the ut_exit.e_exit member.

RETURN VALUES

Upon successful completion, getutxent(), getutxid(), and getutxline()
each return a pointer to a utmpx structure containing a copy of the
requested entry in the user accounting database. Otherwise a null
pointer is returned.

The return value may point to a static area which is overwritten by a
subsequent call to getutxid () or getutxline().

Upon successful completion, pututxline() returns a pointer to a utmpx
structure containing a copy of the entry added to the user accounting
database. Otherwise a null pointer is returned.

The endutxent() and setutxent() functions return no value.

A null pointer is returned upon failure to read, whether for
permissions or having reached the end of file, or upon failure to
write.

USAGE

These functions use buffered standard I/O for input, but pututxline()
uses an unbuffered write to avoid race conditions between processes
trying to modify the utmpx and wtmpx files.

Applications should not access the utmpx and wtmpx databases
directly, but should use these functions to ensure that these
databases are maintained consistently.

FILES

/var/adm/utmpx
user access and accounting information

/var/adm/wtmpx
history of user access and accounting information

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:

+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | See below. |
+--------------------+-----------------+
|MT-Level | Unsafe |
+--------------------+-----------------+

The endutxent(), getutxent(), getutxid(), getutxline(), pututxline(),
and setutxent() functions are Standard.

NOTES

The most current entry is saved in a static structure. Multiple
accesses require that it be copied before further accesses are made.
On each call to either getutxid() or getutxline(), the routine
examines the static structure before performing more I/O. If the
contents of the static structure match what it is searching for, it
looks no further. For this reason, to use getutxline() to search for
multiple occurrences it would be necessary to zero out the static
after each success, or getutxline() would just return the same
structure over and over again. There is one exception to the rule
about emptying the structure before further reads are done. The
implicit read done by pututxline() (if it finds that it is not
already at the correct place in the file) will not hurt the contents
of the static structure returned by the getutxent(), getutxid(), or
getutxline() routines, if the user has just modified those contents
and passed the pointer back to pututxline().

November 21, 2014 GETUTXENT(3C)