|GETUTENT(3)||Linux Programmer's Manual||GETUTENT(3)|
NAMEgetutent, getutid, getutline, pututline, setutent, endutent, utmpname - access utmp file entries
DESCRIPTIONNew applications should use the POSIX.1-specified "utmpx" versions of these functions; see CONFORMING TO.
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. The definition of this structure is shown in utmp(5).
getutid() searches forward from the current file position in the utmp file based upon ut. If ut->ut_type is one of RUN_LVL, BOOT_TIME, NEW_TIME, or OLD_TIME, getutid() will find the first entry whose ut_type field matches ut->ut_type. If ut->ut_type is one of INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS, getutid() will find the first entry whose ut_id field matches ut->ut_id.
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->ut_line.
pututline() writes the utmp structure ut into the utmp file. It uses getutid() to search for the proper place in the file to insert the new entry. If it cannot find an appropriate slot for ut, pututline() will append the new entry to the end of the file.
RETURN VALUEgetutent(), getutid(), and getutline() return a pointer to a struct utmp on success, and NULL on failure (which includes the "record not found" case). This struct utmp is allocated in static storage, and may be overwritten by subsequent calls.
- Out of memory.
- Record not found.
setutent(), pututline(), and the getut* () functions can also fail for the reasons described in open(2).
FILES/var/run/utmp database of currently logged-in users
CONFORMING TOXPG2, SVr4.
In XPG2 and SVID 2 the function pututline() is documented to return void, and that is what it does on many systems (AIX, HP-UX, Linux libc5). HP-UX introduces a new function _pututline() with the prototype given above for pututline() (also found in Linux libc5).
All these functions are obsolete now on non-Linux systems. POSIX.1-2001, following SUSv1, does not have any of these functions, but instead uses
struct utmpx *getutxent(void);
struct utmpx *getutxid(const struct utmpx *);
struct utmpx *getutxline(const struct utmpx *);
struct utmpx *pututxline(const struct utmpx *);
These functions are provided by glibc, and perform the same task as their equivalents without the "x", but use struct utmpx, defined on Linux to be the same as struct utmp. For completeness, glibc also provides utmpxname(), although this function is not specified by POSIX.1.
On some other systems, the utmpx structure is a superset of the utmp structure, with additional fields, and larger versions of the existing fields, and parallel files are maintained, often /var/*/utmpx and /var/*/wtmpx.
Linux glibc on the other hand does not use a parallel utmpx file since its utmp structure is already large enough. The "x" functions listed above are just aliases for their counterparts without the "x" (e.g., getutxent() is an alias for getutent()).
Glibc notesThe above functions are not thread-safe. Glibc adds reentrant versions
#define _GNU_SOURCE /* or _SVID_SOURCE or _BSD_SOURCE;
see feature_test_macros(7) */ #include
int getutent_r(struct utmp * ubuf , struct utmp ** ubufp );
int getutid_r(struct utmp * ut ,
struct utmp * ubuf , struct utmp ** ubufp );
int getutline_r(struct utmp * ut ,
struct utmp * ubuf , struct utmp ** ubufp );
EXAMPLEThe 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(3) and ttyname(3).
main(int argc, char *argv)
struct utmp entry;
system("echo before adding entry:;who");
entry.ut_type = USER_PROCESS;
entry.ut_pid = getpid();
strcpy(entry.ut_line, ttyname(STDIN_FILENO) + strlen("/dev/"));
/* only correct for ptys named /dev/tty[pqr][0-9a-z] */
strcpy(entry.ut_id, ttyname(STDIN_FILENO) + strlen("/dev/tty"));
memset(entry.ut_host, 0, UT_HOSTSIZE);
entry.ut_addr = 0;
system("echo after adding entry:;who");
entry.ut_type = DEAD_PROCESS;
memset(entry.ut_line, 0, UT_LINESIZE);
entry.ut_time = 0;
memset(entry.ut_user, 0, UT_NAMESIZE);
system("echo after removing entry:;who");
SEE ALSOgetutmp(3), utmp(5)
COLOPHONThis page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.