GETPWENT(3) Library Functions Manual GETPWENT(3)
NAME
getpwent, getpwnam, getpwnam_r, getpwuid, getpwuid_r, getpwuuid,
getpwuuid_r, setpassent, setpwent, endpwent – password database
operations
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <pwd.h>
#include <uuid/uuid.h>
struct passwd *
getpwent(void);
struct passwd *
getpwnam(const char *login);
int
getpwnam_r(const char *name, struct passwd *pwd, char *buffer,
size_t bufsize, struct passwd **result);
struct passwd *
getpwuid(uid_t uid);
int
getpwuid_r(uid_t uid, struct passwd *pwd, char *buffer, size_t bufsize,
struct passwd **result);
struct passwd *
getpwuuid(uuid_t uuid);
int
getpwuuid_r(uuid_t uuid, struct passwd *pwd, char *buffer,
size_t bufsize, struct passwd **result);
int
setpassent(int stayopen);
void
setpwent(void);
void
endpwent(void);
DESCRIPTION
These functions obtain information from opendirectoryd(8), including
records in /etc/master.passwd which is described in master.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 access class */
char *pw_gecos; /* Honeywell login info */
char *pw_dir; /* home directory */
char *pw_shell; /* default shell */
time_t pw_expire; /* account expiration */
int pw_fields; /* internal: fields filled in */
};
The functions getpwnam(), getpwuid(), and getpwuuid() search the password
database for the given login name, user uid, or user uuid respectively,
always returning the first one encountered.
Note that the password file /etc/master.passwd does not contain user
UUIDs. The UUID for a user may be found using mbr_uid_to_uuid().
On OS X, these routines are thread-safe and return a pointer to a thread-
specific data structure. The contents of this data structure are
automatically released by subsequent calls to any of these routines on
the same thread, or when the thread exits. These routines are therefore
unsuitable for use in libraries or frameworks, from where they may
overwrite the per-thread data that the calling application expects to
find as a result of its own calls to these routines. Library and
framework code should use the alternative reentrant variants detailed
below.
The getpwent() function searches all available directory services on its
first invocation. It caches the returned entries in a list and returns
user account entries one at a time.
NOTE that getpwent() may cause a very lengthy search for user account
records by opendirectoryd and may result in a large number of user
account records being cached by the calling process. Use of this
function is not advised.
The functions getpwnam_r(), getpwuid_r(), and getpwuuid_r() are
alternative versions of getpwnam(), getpwuid(), and getpwuuid()
respectively. They store the results of their search in the caller-
provided pwd structure, which additionally contains pointers to strings
that are stored in the caller-provided buffer of size bufsize. (The
maximum required bufsize can be obtained by passing the
_SC_GETPW_R_SIZE_MAX constant to the sysconf(3) call. See example code
below.) When these functions are successful, the pwd argument will be
filled in, and a pointer to that argument will be stored in the caller-
provided result. If an entry is not found or an error occurs, result
will be set to NULL.
The setpassent() function causes getpwent() to ``rewind'' to the
beginning of the list of entries cached by a previous getpwent() call.
The cache is not cleared. The stayopen parameter value is unused on OS
X.
The setpwent() and endpwent() functions clear the cached results from a
previous getpwent() call.
These routines have been written to ‘shadow’ the password of user records
created on Mac OS X 10.3 or later, by returning a structure whose
password field points to the string ‘********’. Legacy crypt passwords
are still returned for user records created on earlier versions of Mac OS
X whose opendirectoryd(8) attribute contains the value ‘;basic;’.
Note that opendirectoryd(8) allows user records from some sources which
may not include all the component fields present in a passwd structure.
Only the name, uid, and gid of a user record are required. Default
values will be supplied as follows:
pw_passwd = "*"
pw_change = 0
pw_class = ""
pw_gecos = ""
pw_dir = "/var/empty"
pw_shell = "/usr/bin/false"
pw_expire = 0
RETURN VALUES
The functions getpwent(), getpwnam(), getpwuid(), and getpwuuid() return
a valid pointer to a passwd structure on success or NULL if the entry is
not found or if an error occurs. If an error does occur, errno will be
set. Note that programs must explicitly set errno to zero before calling
any of these functions if they need to distinguish between a non-existent
entry and an error. The functions getpwnam_r(), getpwuid_r(), and
getpwuuid_r() return 0 if no error occurred, or an error number to
indicate failure. It is not an error if a matching entry is not found.
(Thus, if result is NULL and the return value is 0, no matching entry
exists.)
The setpassent() function returns 0 on failure and 1 on success. The
endpwent() and setpwent() functions have no return value.
EXAMPLES
To print the current user's home directory without depending on per-
thread storage:
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <pwd.h>
int bufsize;
if ((bufsize = sysconf(_SC_GETPW_R_SIZE_MAX)) == -1)
abort();
char buffer[bufsize];
struct passwd pwd, *result = NULL;
if (getpwuid_r(getuid(), &pwd, buffer, bufsize, &result) != 0 || !result)
abort();
printf("%s\n", pwd.pw_dir);
FILES
The secure password database file
/etc/master.passwd The current password file
/etc/passwd A Version 7 format password file
ERRORS
These routines may fail for any of the errors specified in open(2),
dbopen(3), socket(2), and connect(2), in addition to the following:
[ERANGE] The buffer specified by the buffer and bufsize
arguments was insufficiently sized to store the
result. The caller should retry with a larger buffer.
SEE ALSO
getlogin(2), getgrent(3), passwd(5), mbr_uid_to_uuid(3,)
opendirectoryd(8), yp(8)
STANDARDS
The getpwent(), getpwnam(), getpwnam_r(), getpwuid(), getpwuid_r(),
setpwent(), and endpwent() functions conform to ISO/IEC 9945-1:1996
(“POSIX.1”).
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 getpwnam_r() and getpwuid_r() functions
appeared in FreeBSD 5.1. The functions getpwuuid() and getpwuuid_r()
appeared in Mac OS X 10.8.
BUGS
The functions getpwent(), getpwnam(), getpwuid(), and getpwuuid(), leave
their results in an internal thread-specific memory and return a pointer
to that object. Subsequent calls to the same function will modify the
same object.
macOS 15.2 October 26, 2011 macOS 15.2