NAME
getutent, getutid, getutline, pututline, setutent, endutent, utmpname - access utmp file entries SYNOPSIS
#include
struct utmp *getutent(void); struct utmp *getutid(struct utmp *ut); struct utmp *getutline(struct utmp *ut); struct utmp *pututline(struct utmp *ut); void setutent(void); void endutent(void); int utmpname(const char *file); DESCRIPTION New applications should use the POSIX.1-specified "utmpx" versions of these functions; see CONFORMING TO.
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 PATHUTMP, 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 func‐ tions. 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->uttype is one of RUNLVL, BOOTTIME, NEWTIME, or OLDTIME, getutid() will find the first entry whose
uttype field matches ut->uttype. If ut->uttype is one of INITPROCESS, LOGINPROCESS, USERPROCESS, or DEADPROCESS, getutid()
will find the first entry whose utid field matches ut->utid. getutline() searches forward from the current file position in the utmp file. It scans entries whose uttype is USERPROCESS or LOGINPROCESS
and returns the first one whose utline field matches ut->utline. 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 VALUE getutent(), 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. On success pututline() returns ut; on failure, it returns NULL.
utmpname() returns 0 if the new name was successfully stored, or -1 on failure. In the event of an error, these functions errno set to indicate the cause. ERRORS ENOMEM Out of memory. ESRCH 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 /var/log/wtmp database of past user logins CONFORMING TO XPG2, 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 proto‐ type 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
#include
struct utmpx *getutxent(void); struct utmpx *getutxid(const struct utmpx *); struct utmpx *getutxline(const struct utmpx *); struct utmpx *pututxline(const struct utmpx *); void setutxent(void); void endutxent(void); 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 pro‐ vides 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()). NOTES Glibc notes The above functions are not thread-safe. Glibc adds reentrant versions
#define GNUSOURCE /* or SVIDSOURCE or BSDSOURCE; see featuretestmacros(7) */
#include
int getutentr(struct utmp *ubuf, struct utmp **ubufp); int getutidr(struct utmp *ut, struct utmp *ubuf, struct utmp **ubufp); int getutliner(struct utmp *ut, struct utmp *ubuf, struct utmp **ubufp); These functions are GNU extensions, analogs of the functions of the same name without the r suffix. The ubuf argument gives these func‐ tions a place to store their result. On success they return 0, and a pointer to the result is written in *ubufp. On error these functions return -1. There are no utmpx equivalents of the above functions. (POSIX.1 does not specify such functions.) EXAMPLE 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(3) and ttyname(3).
#include
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int main(int argc, char *argv[]) { struct utmp entry; system("echo before adding entry:;who"); entry.uttype = USERPROCESS; entry.utpid = getpid(); strcpy(entry.utline, ttyname(STDINFILENO) + strlen("/dev/")); /* only correct for ptys named /dev/tty[pqr][0-9a-z] */ strcpy(entry.utid, ttyname(STDINFILENO) + strlen("/dev/tty")); time(&entry.uttime);
strcpy(entry.utuser, getpwuid(getuid())->pwname); memset(entry.uthost, 0, UTHOSTSIZE); entry.utaddr = 0; setutent(); pututline(&entry); system("echo after adding entry:;who"); entry.uttype = DEADPROCESS; memset(entry.utline, 0, UTLINESIZE); entry.uttime = 0; memset(entry.utuser, 0, UTNAMESIZE); setutent(); pututline(&entry); system("echo after removing entry:;who"); endutent(); exit(EXITSUCCESS); } SEE ALSO getutmp(3), utmp(5) COLOPHON
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2013-04-19 GETUTENT(3)