GETPWENT(3) BSD Programmer's Manual GETPWENT(3)NAME
getpwent, getpwnam, getpwuid, setpassent, setpwent, endpwent, getpwent_r,
getpwnam_r, getpwuid_r, setpassent_r, setpwent_r, endpwent_r - password
database operations
SYNOPSIS
#include <sys/types.h>
#include <pwd.h>
struct passwd *
getpwent(void);
struct passwd *
getpwnam(const char *login);
struct passwd *
getpwuid(uid_t uid);
int
setpassent(int stayopen);
int
setpwent(void);
void
endpwent(void);
struct passwd *
getpwent_r(struct passwd *space, char *buf, int buflen);
int
getpwnam_r(const char *login, struct passwd *space, char *buf,
size_t bufsize, struct passwd **result);
int
getpwuid_r(uid_t uid, struct passwd *space, char *buf, size_t bufsize,
struct passwd **result);
void
setpassent_r(int stayopen);
void
setpwent_r(void);
void
endpwent_r(void);
DESCRIPTION
These functions operate on the password database file 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 access class */
char *pw_gecos; /* Honeywell login info */
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 login name or user uid, respectively, always returning the
first one encountered.
The getpwent() function sequentially reads the password database and is
intended for programs that wish to process the complete list of users.
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 routines. (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open as the database will become out of date if it is updated while the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 identical to setpassent() with an argument of
zero.
The endpwent() function closes any open files.
The ``r-suffixed'' functions getpwent_r(), getpwnam_r(), getpwuid_r(),
setpassent_r(), setpwent_r(), and endpwent_r() are reentrant versions of
their corresponding non-reentrant functions. Those that build a passwd
structure must be provided a pointer space to a structure that will hold
the result, as well as a buffer and its size (buflen or bufsize) for mem-
ory to which members of space may be pointed. The built-up structure
will either be returned directly (getpwent_r()), or stored via the result
parameter. This will be NULL if the given user name or ID does not ex-
ist. For example:
struct passwd space, *pp;
int error;
char buf[SIZE]; /* where SIZE >= sysconf(_SC_GETPW_R_SIZE_MAX) */
error = getpwnam_r(username, &space, buf, sizeof buf, &pp);
if (pp != NULL) {
/* user exists; pp == &space */
printf("user %s, uid %ld\n", pp->pw_name, (long)pp->pw_uid);
} else
... user does not exist, or an error occurred ...
These routines 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(), getpwent_r(), getpwnam(), and getpwuid() return
a valid pointer to a passwd structure on success and a null pointer if
end-of-file is reached or an error occurs. The functions getpwnam_r()
and getpwuid_r() return 0 on success, or an error number on failure. The
functions setpassent() and setpwent() return 0 on failure and 1 on suc-
cess. The functions endpwent(), setpwent_r(), and endpwent_r() have no
return value.
If the buffer supplied to the reentrant functions is too small, they will
fail with an ERANGE error. The POSIX functions getpwnam_r() and
getpwuid_r() will return ERANGE, while getpwent_r() will set the global
variable errno instead.
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
SEE ALSOgetlogin(2), getgrent(3), passwd(5), pwd_mkdb(8), vipw(8)HISTORY
The getpwent, getpwnam, getpwuid, setpwent, and endpwent functions ap-
peared in Version 7 AT&T UNIX. The setpassent function appeared in
4.3BSD-Reno.
BUGS
The functions getpwent(), getpwnam(), and getpwuid(), leave their results
in an internal static object and return a pointer to that object. Subse-
quent calls to the same function will modify the same object.
The routines getpwent(), endpwent(), setpassent(), and setpwent() are
fairly useless in a networked environment and should be avoided, if pos-
sible.
The getpwent(), endpwent(), setpassent(), and setpwent() functions may
not be safely called concurrently from multiple threads, e.g., the inter-
faces described by pthreads(3).
The non-standard functions setpwent(), setpassent_r(), setpwent_r(),
getpwent_r(), and endpwent_r() are known to have different interfaces on
different systems, and should probably be avoided.
The ``interesting'' calling sequences for the reentrant functions are
courtesy of ongoing standardization efforts.
COMPATIBILITY
The historic function setpwfile(3), which allowed the specification of
alternate password databases, has been deprecated and is no longer avail-
able.
The getpwnam(), getpwuid(), getpwnam_r(), and getpwuid_r(), functions
conform to IEEE Std1003.1-1996 (``POSIX'').
BSDI BSD/OS April 27, 2001 3
