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/* GNU's read utmp module.
Copyright (C) 1992-2001, 2003-2006, 2009-2020 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by jla; revised by djm */
#include <config.h>
#include "readutmp.h"
#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <signal.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include "xalloc.h"
#if USE_UNLOCKED_IO
# include "unlocked-io.h"
#endif
#if 8 <= __GNUC__
# pragma GCC diagnostic ignored "-Wsizeof-pointer-memaccess"
#endif
/* Copy UT->ut_name into storage obtained from malloc. Then remove any
trailing spaces from the copy, NUL terminate it, and return the copy. */
char *
extract_trimmed_name (const STRUCT_UTMP *ut)
{
char *p, *trimmed_name;
trimmed_name = xmalloc (sizeof (UT_USER (ut)) + 1);
strncpy (trimmed_name, UT_USER (ut), sizeof (UT_USER (ut)));
/* Append a trailing NUL. Some systems pad names shorter than the
maximum with spaces, others pad with NULs. Remove any trailing
spaces. */
trimmed_name[sizeof (UT_USER (ut))] = '\0';
for (p = trimmed_name + strlen (trimmed_name);
trimmed_name < p && p[-1] == ' ';
*--p = '\0')
continue;
return trimmed_name;
}
/* Is the utmp entry U desired by the user who asked for OPTIONS? */
static bool
desirable_utmp_entry (STRUCT_UTMP const *u, int options)
{
bool user_proc = IS_USER_PROCESS (u);
if ((options & READ_UTMP_USER_PROCESS) && !user_proc)
return false;
if ((options & READ_UTMP_CHECK_PIDS)
&& user_proc
&& 0 < UT_PID (u)
&& (kill (UT_PID (u), 0) < 0 && errno == ESRCH))
return false;
return true;
}
/* Read the utmp entries corresponding to file FILE into freshly-
malloc'd storage, set *UTMP_BUF to that pointer, set *N_ENTRIES to
the number of entries, and return zero. If there is any error,
return -1, setting errno, and don't modify the parameters.
If OPTIONS & READ_UTMP_CHECK_PIDS is nonzero, omit entries whose
process-IDs do not currently exist. */
#ifdef UTMP_NAME_FUNCTION
int
read_utmp (char const *file, size_t *n_entries, STRUCT_UTMP **utmp_buf,
int options)
{
size_t n_read = 0;
size_t n_alloc = 0;
STRUCT_UTMP *utmp = NULL;
STRUCT_UTMP *u;
/* Ignore the return value for now.
Solaris' utmpname returns 1 upon success -- which is contrary
to what the GNU libc version does. In addition, older GNU libc
versions are actually void. */
UTMP_NAME_FUNCTION ((char *) file);
SET_UTMP_ENT ();
while ((u = GET_UTMP_ENT ()) != NULL)
if (desirable_utmp_entry (u, options))
{
if (n_read == n_alloc)
utmp = x2nrealloc (utmp, &n_alloc, sizeof *utmp);
utmp[n_read++] = *u;
}
END_UTMP_ENT ();
*n_entries = n_read;
*utmp_buf = utmp;
return 0;
}
#else
int
read_utmp (char const *file, size_t *n_entries, STRUCT_UTMP **utmp_buf,
int options)
{
size_t n_read = 0;
size_t n_alloc = 0;
STRUCT_UTMP *utmp = NULL;
int saved_errno;
FILE *f = fopen (file, "r");
if (! f)
return -1;
for (;;)
{
if (n_read == n_alloc)
utmp = x2nrealloc (utmp, &n_alloc, sizeof *utmp);
if (fread (&utmp[n_read], sizeof utmp[n_read], 1, f) == 0)
break;
n_read += desirable_utmp_entry (&utmp[n_read], options);
}
saved_errno = ferror (f) ? errno : 0;
if (fclose (f) != 0)
saved_errno = errno;
if (saved_errno != 0)
{
free (utmp);
errno = saved_errno;
return -1;
}
*n_entries = n_read;
*utmp_buf = utmp;
return 0;
}
#endif
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