void setutent(void); void endutent(void);
utmpname() sets the name of the utmp-format file for the other utmp functions to access. If utmpname() is not used to set the filename before the other functions are used, they assume _PATH_UTMP, as defined in .
setutent() rewinds the file pointer to the beginning of the utmp file. It is generally a Good Idea to call it before any of the other functions.
endutent() closes the utmp file. It should be called when the user code is done accessing the file with the other functions.
getutent() reads a line from the current file position in the utmp file. It returns a pointer to a structure containing the fields of the line.
getutid() searches forward from the current file position in the utmp file based upon ut. If ut- is RUN_LVL, BOOT_TIME, NEW_TIME, or OLD_TIME, getutid() will find the first entry whose ut_type field matches ut-. If ut- is one of INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS, getutid() will find the first entry whose ut_id field matches ut-.
getutline() searches forward from the current file position in the utmp file. It scans entries whose ut_type is USER_PROCESS or LOGIN_PROCESS and returns the first one whose ut_line field matches ut-.
The following example adds and removes a utmp record, assuming it is run from within a pseudo terminal. For usage in a real application, you should check the return values of getpwuid() and ttyname().