getutent(3)getutent(3)NAME
getutent, getutent_r, getutid, getutid_r, getutline, getutline_r,
pututline, pututline_r, setutent, setutent_r, endutent, endutent_r,
utmpname - Access utmp file entries
SYNOPSIS
#include <utmp.h>
struct utmp *getutent(
void ); struct utmp *getutid(
struct utmp *id ); struct utmp *getutline(
struct utmp *line ); struct utmp *pututline(
struct utmp *utmp_ptr ); void setutent(
void ); void endutent(
void ); void utmpname(
char *file );
The following functions are supported in order to maintain backward
compatibility with previous versions of the operating system.
int getutent_r(
struct utmp **utmp,
struct utmp_data *utmp_data ); int getutid_r(
struct utmp *id,
struct utmp **utmp,
struct utmp_data *utmp_data ); int getutline_r(
struct utmp *line,
struct utmp **utmp,
struct utmp_data *utmp_data ); int pututline_r(
struct utmp *utmp_ptr,
struct utmp_data *utmp_data ); void setutent_r(
struct utmp_data *utmp_data ); void endutent_r(
struct utmp_data *utmp_data );
LIBRARY
Standard C Library (libc)
PARAMETERS
Specifies one of the RUN_LVL, BOOT_TIME, OLD_TIME, NEW_TIME,
INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS entries.
If id is one of the RUN_LVL, BOOT_TIME, OLD_TIME, or NEW_TIME
entries, the getutid() function searches forward from the cur‐
rent point in the utmp file until an entry with a ut_type match‐
ing id->ut_type is found.
If id is one of the INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS,
or DEAD_PROCESS entries, the getutid() function returns 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 the file is
reached without a match, the getutid() function fails. Matches
a utmp entry of the type LOGIN_PROCESS or USER_PROCESS such that
the ut_line matches \%line->ut_line. The getutline() function
searches from the current point in the utmp file until it finds
a matching line. If the end the of file is reached without a
match, the getutline() function fails. Points to a utmp struc‐
ture to be placed into the utmp file. Specifies the name of the
file to be examined. Points at the returned utmp structure. Is
the data for the utmp database.
DESCRIPTION
The getutent(), getutid(), and getutline() functions return a pointer
to a utmp structure.
The getutent() function reads the next entry from a file similar to the
utmp file. If the file is not already open, the getutent() function
opens it. If the file does not exist, getutent() tries to create a
file. The getutent() function fails and returns a null pointer if one
or more of the following occur: The end of the file is reached. The
file creation fails. The read or write file permissions are inappro‐
priate.
The pututline() function writes the supplied utmp_ptr parameter struc‐
ture into the utmp file. If you have not searched for the proper place
in the file using one of the getut... routines, the pututline() func‐
tion calls getutid() to search forward for the proper place. It is
expected that the user of pututline() searched for the proper entry
using one of the getut... functions. If so, pututline() does not
search. If the pututline() function does not find a matching slot for
the entry, it adds a new entry to the end of the file. Note that the
pututline() function waits for a short time before it decides that the
current process holding the lock is dead and proceeds to write to the
file.
The setutent() function resets the input stream to the beginning of the
file. You should do this before each search for a new entry if you want
to examine the entire file.
The endutent() function closes the currently open file.
The utmpname() function changes the name of the file to be examined
from /var/adm/utmp to any other filename. The name specified is usu‐
ally /var/adm/wtmp. If the specified file does not exist, no indication
is given until the file is referenced. The utmpname() function does
not open the file, but closes the old file (if it is currently open)
and saves the new filename.
The most current entry is saved in a static structure, making the utmp‐
name() function non-reentrant. To make multiple accesses, you must copy
or use the structure between each access. The getutid() and getutline()
functions examine the static structure first. If the contents of the
static structure match what they are searching for, they do not read
the utmp file. Therefore, you must fill the static structure with zeros
after each use if you want to use these subroutines to search for mul‐
tiple occurrences.
If the pututline() function finds that it is not already at the correct
place in the file, the implicit read it performs does not overwrite the
contents of the static structure returned by the getutent(), getutid(),
or getutline() functions. This allows you to get an entry with one of
these subroutines, modify the structure, and pass the pointer back to
the pututline() function for writing.
These functions use buffered standard I/O for input, but the putut‐
line() function uses an unbuffered nonstandard write to avoid race con‐
ditions between processes trying to modify the utmp and wtmp files and
uses the flock system call.
The getutent_r(), getutid_r(), getutline_r(), pututline_r(), setut‐
line_r(), and endutline_r() functions are the reentrant versions of the
getutent(), getutid(), getutline(), pututline(), setutline(), and
endutline() functions. They are supported in order to maintain backward
compatibility with previous versions of the operating system.
Upon successful completion, the getutent_r(), getutid_r(), and getut‐
line_r() functions provide a pointer to the utmp structure in utmp.
Otherwise, they return a value of -1. The utmp.h header file defines
the utmp_data structure.
NOTES
The utmpname() function does not close any file streams when used for
reentrant applications.
The utmpname() function is a function that returns void. If it is given
a file parameter that exceeds the maximum path length, the function
simply returns and does not change the filename.
Note that before accessing the utmp file for the first time, the ut_fd
field of the utmp_data structure must be set to a value of -1.
When compiling, calls to the getutent(), getutid(), getutline(), putut‐
line(), getutent_r(), getutid_r(), getutline_r(), pututline_r(), endu‐
tent_r(), and setutent_r() functions are internally renamed by prepend‐
ing _E to the function name. When debugging a module that includes
these functions, use _Egetutent to refer to the getutent() call.
RETURN VALUES
Upon successful completion, the getutent(), getutid(), and getutline()
functions return pointers to the utmp structure. If a read or write
fails due to the end of the file or due to a permission conflict, the
getutent(), getutid(), getutline(), and pututline() functions fail and
return a null pointer.
The getutent_r(), getutxent_r(), and pututline_r() functions return 0
(zero) on success.
The getutid() function may also fail if the ID is invalid, as does the
getutid_r() function.
ERRORS
The getutent_r(), getutid_r(), and getutline_r() functions set errno to
the corresponding value if any of the following conditions occurs:
Either the utmp, ID, line, or utmp_data parameter is invalid.
The getutid_r() and getutline_r() functions set errno to the corre‐
sponding value if the following condition occurs: The search failed.
The pututline() and pututline_r() functions may fail and set errno to
the corresponding value if the following condition occurs: The process
does not have the appropriate privileges.
FILES
Accounting header file that defines the format for the login database
file. The active login/logoff database files.
SEE ALSO
Commands: wtmpconvert(8)
Functions: flock(2), open(2)
Files: utmp(4), wtmp(4)getutent(3)
