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Name

Synopsis

struct utmp *getutent(void);
struct utmp *getutid(const struct utmp *id);
struct utmp *getutline(const struct utmp *line);
struct utmp *pututline(const struct utmp *utmp);
void setutent(void);
void endutent(void);
int utmpname(const char *file);

MT-Level

Description

char	ut_user[8];	/* user login name */
char	ut_id[4];	/* /sbin/inittab id */
		/* (usually line #) */
char	ut_line[12];	/* device name (console, lnxx) */
short	ut_pid;	/* process id */
short	ut_type;	/* type of entry */
struct exit_status	ut_exit;	/* exit status of a process */
		/* marked as DEAD_PROCESS */
time_t	ut_time;	/* time entry was made */

The structure exit status includes the following members:

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

getutent() reads in the next entry from a utmp-like file. If the file is not already open, it opens it. If it reaches the end of the file, it fails.

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

getutline() searches forward from the current point in the utmp file until it finds an entry of the type LOGIN_PROCESS or ut_line string matching the line->ut_line string. If the end of file is reached without a match, it fails.

pututline() writes out the supplied utmp structure into the utmp file. It uses getutid() 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 pututline() will have searched for the proper entry using one of the these routines. If so, pututline() will not search. If pututline() does not find a matching slot for the new entry, it will add a new entry to the end of the file. It returns a pointer to the utmp structure. When called by a non-root user, pututline() invokes a setuid() root program to verify and write the entry, since /etc/utmp is normally writable only by root. In this event, the ut_name field must correspond to the actual user name associated with the process; the ut_type field must be either USER_PROCESS or DEAD_PROCESS ; and the ut_line field must be a device special file and be writable by the user.

setutent() resets the input stream to the beginning of the file. This reset should be done before each search for a new entry if it is desired that the entire file be examined.

endutent() closes the currently open file.

utmpname() allows the user to change the name of the file examined, from /var/adm/utmp to any other file. It is most often expected that this other file will be /var/adm/wtmp. If the file does not exist, this will not be apparent until the first attempt to reference the file is made. utmpname() does not open the file. It just closes the old file if it is currently open and saves the new file name.

Return Values

A null pointer is returned upon failure to read, whether for permissions or having reached the end of file, or upon failure to write. If the file name given is longer than 79 characters, utmpname() returns 0. Otherwise, it returns 1.

Files

/var/adm/utmp

/var/adm/wtmp

See Also

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 getutid() or getutline(), 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 getutline() to search for multiple occurrences, it would be necessary to zero out the static area after each success, or getutline() 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 pututline() (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 getutent(), getutid() or getutline() routines, if the user has just modified those contents and passed the pointer back to pututline().

These routines use buffered standard I/O for input, but pututline() uses an unbuffered non-standard write to avoid race conditions between processes trying to modify the utmp and wtmp

Table of Contents

• Name
• Synopsis
• MT-Level
• Description
• Return Values
• Files
• See Also
• Notes