man pages section 3: Basic Library Functions

Exit Print View

Updated: July 2014
 
 

pututxline(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(4)). 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(1M), 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 nonuser() and nonuserx() macros use the 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_USER 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(5) 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.

See Also

getutent(3C), ttyslot(3C), wait(3C), wait.h(3HEAD), utmpx(4), attributes(5), standards(5)

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().