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[thirdparty/man-pages.git] / man3 / getutent.3

.\" Copyright 1995 Mark D. Roth (roth@uiuc.edu)
.\"
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.\"     Linux libc source code
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.\" Modified Thu Jul 25 14:43:46 MET DST 1996 by Michael Haardt <michael@cantor.informatik.rwth-aachen.de>
.\"
.TH GETUTENT 3 1996-07-25 "" "Library functions"
.SH NAME
getutent, getutid, getutline, pututline, setutent, endutent, utmpname \- access utmp file entries
.SH SYNOPSIS
.B #include <utmp.h>
.sp
.B struct utmp *getutent(void);
.br
.BI "struct utmp *getutid(struct utmp *" ut );
.br
.BI "struct utmp *getutline(struct utmp *" ut );
.sp
.BI "struct utmp *pututline(struct utmp *" ut );
.sp
.B void setutent(void);
.br
.B void endutent(void);
.sp
.BI "void utmpname(const char *" file );
.SH DESCRIPTION
\fButmpname\fP() sets the name of the utmp-format file for the other utmp
functions to access.  If \fButmpname\fP() is not used to set the filename
before the other functions are used, they assume \fB_PATH_UTMP\fP, as
defined in \fI<paths.h>\fP.
.PP
\fBsetutent\fP() 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.
.PP
\fBendutent\fP() closes the utmp file.  It should be called when the user
code is done accessing the file with the other functions.
.PP
\fBgetutent\fP() 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.
.PP
\fBgetutid\fP() searches forward from the current file position in the utmp
file based upon \fIut\fP.  If \fIut\fP->ut_type is one of \fBRUN_LVL\fP,
\fBBOOT_TIME\fP, \fBNEW_TIME\fP, or \fBOLD_TIME\fP, \fBgetutid\fP() will
find the first entry whose \fIut_type\fP field matches \fIut\fP->ut_type.
If \fIut\fP->ut_type is one of \fBINIT_PROCESS\fP, \fBLOGIN_PROCESS\fP,
\fBUSER_PROCESS\fP, or \fBDEAD_PROCESS\fP, \fBgetutid\fP() will find the
first entry whose ut_id field matches \fIut\fP->ut_id.
.PP
\fBgetutline\fP() searches forward from the current file position in the
utmp file.  It scans entries whose ut_type is \fBUSER_PROCESS\fP
or \fBLOGIN_PROCESS\fP and returns the first one whose ut_line field
matches \fIut\fP->ut_line.
.PP
\fBpututline\fP() writes the utmp structure \fIut\fP into the utmp file.  It
uses \fBgetutid\fP() to search for the proper place in the file to insert
the new entry.  If it cannot find an appropriate slot for \fIut\fP,
\fBpututline\fP() will append the new entry to the end of the file.
.SH "RETURN VALUE"
\fBgetutent\fP(), \fBgetutid\fP(), \fBgetutline\fP() and \fBpututline\fP()
return a pointer to a \fBstruct utmp\fP on success, and NULL on failure.
This \fBstruct utmp\fP is allocated in static storage, and may be
overwritten by subsequent calls.
.SH "REENTRANT VERSIONS"
These above functions are not thread-safe. Glibc adds reentrant versions
.sp
.nf
.BR "#define _GNU_SOURCE" "    /* or _SVID_SOURCE or _BSD_SOURCE */
.B #include <utmp.h>
.sp
.BI "int getutent_r(struct utmp *" ubuf ", struct utmp **" ubufp );
.sp
.BI "int getutid_r(struct utmp *" ut ,
.BI "              struct utmp *" ubuf ", struct utmp **" ubufp );
.sp
.BI "int getutline_r(struct utmp *" ut ,
.BI "                struct utmp *" ubuf ", struct utmp **" ubufp );
.fi
.sp
These functions are GNU extensions, analogs of the functions of the
same name without the _r suffix. The
.I ubuf
parameter gives these functions a place to store their result.
On success they return 0, and a pointer to the result is written in
.RI * ubufp .
On error these functions return \-1.
.SH 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() and ttyname().
.PP
.nf
#include <string.h>
#include <stdlib.h>
#include <pwd.h>
#include <unistd.h>
#include <utmp.h>

int 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(0)+strlen("/dev/"));
  /* only correct for ptys named /dev/tty[pqr][0\-9a\-z] */
  strcpy(entry.ut_id,ttyname(0)+strlen("/dev/tty"));
  time(&entry.ut_time);
  strcpy(entry.ut_user,getpwuid(getuid())\->pw_name);
  memset(entry.ut_host,0,UT_HOSTSIZE);
  entry.ut_addr=0;
  setutent();
  pututline(&entry);

  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);
  setutent();
  pututline(&entry);

  system("echo after removing entry:;who");

  endutent();
  return 0;
}
.fi
.SH FILES
/var/run/utmp	database of currently logged-in users
.br
/var/log/wtmp	database of past user logins
.SH "CONFORMING TO"
XPG 2, SVID 2, Linux FSSTND 1.2
.LP
In XPG2 and SVID2  the function \fIpututline\fP() is documented
to return void, and that is what it does on many systems
(AIX, HPUX, Linux libc5).
HPUX introduces a new function \fI_pututline\fP() with the prototype
given above for \fIpututline\fP() (also found in Linux libc5).
.LP
All these functions are obsolete now on non-Linux systems.
POSIX 1003.1-2001, following XPG4.2,
does not have any of these functions, but instead uses
.sp
.B #include <utmpx.h>
.sp
.B struct utmpx *getutxent(void);
.br
.B struct utmpx *getutxid(const struct utmpx *);
.br
.B struct utmpx *getutxline(const struct utmpx *);
.br
.B struct utmpx *pututxline(const struct utmpx *);
.br
.B void setutxent(void);
.br
.B void endutxent(void);
.sp
The \fIutmpx\fP structure is a superset of the \fIutmp\fP structure,
with additional fields, and larger versions of the existing fields.
The corresponding files are often
.I /var/*/utmpx
and
.IR /var/*/wtmpx .
.LP
Linux glibc on the other hand does not use \fIutmpx\fP since its
\fIutmp\fP structure is already large enough. The functions \fIgetutxent\fP
etc. are aliases for \fIgetutent\fP etc.
.SH "SEE ALSO"
.BR utmp (5)