diff options
Diffstat (limited to 'login/pututline_r.c')
-rw-r--r-- | login/pututline_r.c | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/login/pututline_r.c b/login/pututline_r.c new file mode 100644 index 0000000..365a376 --- /dev/null +++ b/login/pututline_r.c @@ -0,0 +1,89 @@ +/* Copyright (C) 1996 Free Software Foundation, Inc. +This file is part of the GNU C Library. +Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996. + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +The GNU C Library 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, +Boston, MA 02111-1307, USA. */ + +#include <alloca.h> +#include <errno.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <utmp.h> +#include <sys/file.h> + + +int +pututline_r (const struct utmp *utmp_ptr, struct utmp_data *utmp_data) +{ + /* Open utmp file if not already done. */ + if (utmp_data->ut_fd == -1) + { + setutent_r (utmp_data); + if (utmp_data->ut_fd == -1) + return -1; + } + + /* Seek position to write. */ + if (utmp_data->ubuf.ut_type != utmp_ptr->ut_type) + { + /* We must not overwrite the data in UTMP_DATA. */ + struct utmp_data *data_tmp = alloca (sizeof (utmp_data)); + struct utmp *dummy; + + memcpy (data_tmp, utmp_data, sizeof (utmp_data)); + utmp_data = data_tmp; + + if (getutid_r (utmp_ptr, &dummy, utmp_data) < 0) + { + if (errno != ESRCH) + return -1; + + utmp_data->loc_utmp = lseek (utmp_data->ut_fd, 0, SEEK_END); + if (utmp_data->loc_utmp == -1) + return -1; + } + } + + /* Position file correctly. */ + if (utmp_data->loc_utmp > 0 + && lseek (utmp_data->ut_fd, utmp_data->loc_utmp - sizeof (struct utmp), + SEEK_SET) < 0) + return -1; + + /* XXX An alternative solution would be to call an SUID root program + which write the new value. */ + + /* Try to lock the file. */ + if (flock (utmp_data->ut_fd, LOCK_EX | LOCK_NB) < 0 && errno != ENOSYS) + { + /* Oh, oh. The file is already locked. Wait a bit and try again. */ + sleep (1); + + /* This time we ignore the error. */ + (void) flock (utmp_data->ut_fd, LOCK_EX | LOCK_NB); + } + + /* Write the new data. */ + if (write (utmp_data->ut_fd, &utmp_data->ubuf, sizeof (struct utmp)) + != sizeof (struct utmp)) + return -1; + + /* And unlock the file. */ + (void) flock (utmp_data->ut_fd, LOCK_UN); + + return 0; +} |