NAME
getpwent
,
getpwent_r
, getpwnam
,
getpwnam_r
, getpwuid
,
getpwuid_r
, setpassent
,
setpwent
, endpwent
—
password database operations
LIBRARY
library “libc”
SYNOPSIS
#include
<pwd.h>
struct passwd *
getpwent
(void);
int
getpwent_r
(struct passwd *pw,
char *buffer, size_t buflen,
struct passwd **result);
struct passwd *
getpwnam
(const
char *name);
int
getpwnam_r
(const char *name,
struct passwd *pw, char *buffer,
size_t buflen, struct passwd
**result);
struct passwd *
getpwuid
(uid_t
uid);
int
getpwuid_r
(uid_t uid,
struct passwd *pw, char *buffer,
size_t buflen, struct passwd
**result);
int
setpassent
(int
stayopen);
void
setpwent
(void);
void
endpwent
(void);
DESCRIPTION
These functions operate on the password database which is described in passwd(5). Each entry in the database is defined by the structure passwd found in the include file<pwd.h>
:
struct passwd { char *pw_name; /* user name */ char *pw_passwd; /* encrypted password */ uid_t pw_uid; /* user uid */ gid_t pw_gid; /* user gid */ time_t pw_change; /* password change time */ char *pw_class; /* user login class */ char *pw_gecos; /* general information */ char *pw_dir; /* home directory */ char *pw_shell; /* default shell */ time_t pw_expire; /* account expiration */ };
The functions
getpwnam
()
and
getpwuid
()
search the password database for the given user name pointed to by
name or user id pointed to by
uid respectively, always returning the first one
encountered. Identical user names or user ids may result in undefined
behavior.
The
getpwent
()
function sequentially reads the password database and is intended for
programs that wish to process the complete list of users.
The functions
getpwnam_r
(),
getpwuid_r
(),
and
getpwent_r
()
act like their non re-entrant counterparts, updating the contents of
pw and storing a pointer to that in
result, and returning 0
.
Storage used by pw is allocated from
buffer, which is buflen bytes in
size. If the requested entry cannot be found, result
will point to NULL
and 0
will be returned. If an error occurs, a non-zero error number will be
returned and result will point to
NULL
. Calling getpwent_r
()
from multiple threads will result in each thread reading a disjoint portion
of the password database.
The
setpassent
()
function accomplishes two purposes. First, it causes
getpwent
() to “rewind” to the
beginning of the database. Additionally, if stayopen
is non-zero, file descriptors are left open, significantly speeding up
subsequent accesses for all of the functions. (This latter functionality is
unnecessary for getpwent
() as it doesn't close its
file descriptors by default.)
It is dangerous for long-running programs to keep the file descriptors open as the database will become out of date if it is updated while the program is running.
The
setpwent
()
function is equivalent to setpassent
() with an
argument of zero.
The
endpwent
()
function closes any open files.
These functions have been written to “shadow” the
password file, e.g. allow only certain programs to have access to the
encrypted password. If the process which calls them has an effective uid of
0, the encrypted password will be returned, otherwise, the password field of
the returned structure will point to the string
‘*
’.
RETURN VALUES
The functions getpwent
(),
getpwnam
(), and getpwuid
(),
return a valid pointer to a passwd structure on success and a
NULL
pointer if the entry was not found or an error
occurred. If an error occurred, the global variable
errno
is set to indicate the nature of the failure.
The setpassent
() function returns 0 on failure,
setting the global variable errno
to indicate the
nature of the failure, and 1 on success. The
endpwent
() and setpwent
()
functions have no return value. The functions
getpwnam_r
(), getpwuid_r
(),
and getpwent_r
() return 0
on
success or entry not found, and non-zero on failure, setting the global
variable errno
to indicate the nature of the
failure.
FILES
- /etc/pwd.db
- The insecure password database file
- /etc/spwd.db
- The secure password database file
- /etc/master.passwd
- The current password file
- /etc/passwd
- A Version 7 format password file
COMPATIBILITY
The historic function setpwfile
() which
allowed the specification of alternative password databases, has been
deprecated and is no longer available.
ERRORS
The following error codes may be set in
errno for getpwent
,
getpwent_r
, getpwnam
,
getpwnam_r
, getpwuid
,
getpwuid_r
, and
setpassent
:
- [
EINTR
] - A signal was caught during the database search.
- [
EIO
] - An I/O error has occurred.
- [
EMFILE
] - The limit on open files for this process has been reached.
- [
ENFILE
] - The system limit on open files has been reached.
The following error code may be set in errno
for getpwent_r
, getpwnam_r
,
and getpwuid_r
:
- [
ERANGE
] - The resulting struct passwd does not fit in the
space defined by
buffer
andbuflen
.
Other errno
values may be set depending on
the specific database backends.
SEE ALSO
getlogin(2), getgrent(3), nsswitch.conf(5), passwd(5), passwd.conf(5), pwd_mkdb(8), vipw(8)
STANDARDS
The getpwnam
() and
getpwuid
(), functions conform to
IEEE Std 1003.1-1990 (“POSIX.1”). The
getpwnam_r
() and
getpwuid_r
() functions conform to
IEEE Std 1003.1c-1995 (“POSIX.1c”).
The endpwent
(), getpwent
(),
and setpwent
() functions conform to
X/Open Portability Guide Issue 4, Version 2
(“XPG4.2”) and IEEE Std 1003.1-2004
(“POSIX.1”) (XSI extension).
HISTORY
The getpwent
,
getpwnam
, getpwuid
,
setpwent
, and endpwent
functions appeared in Version 7 AT&T
UNIX. The setpassent
function appeared in
4.3BSD-Reno. The functions
getpwnam_r
() and
getpwuid_r
() appeared in NetBSD
3.0.
BUGS
The functions getpwent
(),
getpwnam
(), and getpwuid
(),
leave their results in an internal static object and return a pointer to
that object. Subsequent calls to any of these functions will modify the same
object.
The functions getpwent
(),
endpwent
(), setpassent
(),
and setpwent
() are fairly useless in a networked
environment and should be avoided, if possible.
getpwent
() makes no attempt to suppress duplicate
information if multiple sources are specified in
nsswitch.conf(5).