getut(3C)
NAME
getutent(), getutid(), getutline(), pututline(), _pututline(), setutent(), endutent(), utmpname() − access utmp file entry
SYNOPSIS
#include <utmp.h>
struct utmp *getutent(void);
struct utmp *getutid(struct utmp *id);
struct utmp *getutline(struct utmp *line);
struct utmp *_pututline(const struct utmp *utmp);
void pututline(const struct utmp *utmp);
void setutent(void);
void endutent(void);
void utmpname(const char *file);
DESCRIPTION
getutent(), getutid(), and getutline() each return a pointer to a structure of the following type:
struct utmp {
char ut_user[8]; /* User login name */
char ut_id[4]; /* /etc/inittab id (usually line #) */
char ut_line[12]; /* device name (console, lnxx) */
pid_t ut_pid; /* process id */
short ut_type; /* type of entry */
struct exit_status {
short e_termination; /* Process termination status */
short e_exit; /* Process exit status */
} ut_exit; /* The exit status of a process */
/* marked as DEAD_PROCESS. */
unsigned short ut_reserved1; /* Reserved for future use */
time_t ut_time; /* time entry was made */
char ut_host[16]; /* host name, if remote; NOT SUPPORTED */
unsigned long ut_addr; /* Internet addr of host, if remote */
};
getutent() Reads in the next entry from a utmp-like file. If the file is not already open, getutent() opens it. If it reaches the end of the file, getutent() 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, getutid() returns a pointer to the first entry whose type is one of these four, and whose ut_id field matches id−>ut_id. If end-of-file is reached without a match, getutid() fails.
getutline() Searches forward from the current point in the utmp file until it finds an entry of type LOGIN_PROCESS or USER_PROCESS that also has a ut_line string matching the line−>ut_line string. If end-of-file is reached without a match, getutline() fails.
pututline() Writes out the supplied utmp structure into the utmp file. pututline() uses getutid() to search forward for the proper location if it is not already there. It is normally expected that the application program has already searched for the proper entry by using one of the getut() routines before calling pututline(). If the search as already been made, pututline() does not repeat it. If pututline() does not find a matching slot for the new entry, it adds a new entry to the end of the file.
_pututline() Performs the same actions as pututline(), except that it returns a value useful for error checking.
setutent() Resets the input stream to the beginning of the file. This 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 being examined from /etc/utmp to any other file. The other file is usually /etc/wtmp. If the file does not exist, its absence is not discovered until the first subsequent attempt to reference the file. utmpname() does not open the file — it merely closes the old file if it is currently open, and saves the new file name.
The most current entry is saved in a static structure. Multiple accesses require that the structure be copied before further accesses are made. During each call to either getutid() or getutline(), the static structure is examined before performing more I/O. If the contents of the static structure match what the routine is searching for, no additional searching is done. Therefore, if using getutline() to search for multiple occurrences, it is necessary to zero out the static structure after each success; otherwise getutline() simply returns the same pointer over and over again. There is one exception to the rule about removing the structure before a new read: The implicit read done by pututline() (if it finds that it is not already at the correct place in the file) does not alter the contents of the static structure returned by getutent(), getutid(), or getutline() if the user has just modified those contents and passed the pointer back to pututline().
RETURN VALUE
These functions return a NULL pointer upon failure to read (whether for permissions or having reached end-of-file), or upon failure to write. They also return a NULL pointer if the size of the file is not an integral multiple of sizeof(struct utmp).
_pututline() behaves the same as pututline(), except that it returns a pointer to a static location containing the most current utmp entry if the _pututline() call succeeds. The contents of this structure is identical to the contents of the supplied utmp structure if successful. If _pututline() fails, it returns a NULL pointer.
WARNINGS
Some vendors’ versions of getutent() erase the utmp file if the file exists but is not an integral multiple of sizeof(struct utmp). Given the possiblity of user error in providing a name to utmpname (such as giving improper arguments to who(1)), HP-UX does not do this, but instead returns an error indication.
FILES
/etc/utmp
/etc/wtmp
SEE ALSO
STANDARDS CONFORMANCE
endutent(): SVID2, XPG2
getutent(): SVID2, XPG2
getutid(): SVID2, XPG2
getutline(): SVID2, XPG2
pututline(): SVID2, XPG2
setutent(): SVID2, XPG2
utmpname(): SVID2, XPG2
Hewlett-Packard Company — HP-UX Release 9.0: August 1992