GETPWENT(3) BSD Library Functions Manual GETPWENT(3)NAME
getpwent, getpwent_r, getpwnam, getpwnam_r, getpwuid, getpwuid_r,
setpassent, setpwent, endpwent — password database operations
LIBRARY
Standard C Library (libc, -lc)
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 allo‐
cated 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 occured. If an error occured, the global vari‐
able 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 and buflen
Other errno values may be set depending on the specific database back‐
ends.
SEE ALSOgetlogin(2), getgrent(3), nsswitch.conf(5), passwd(5), passwd.conf(5),
pwd_mkdb(8), vipw(8)STANDARDS
The getpwnam() and getpwuid(), functions conform to ISO/IEC 9945-1:1990
(“POSIX.1”). The getpwnam_r() and getpwuid_r() functions conform to IEEE
Std 1003.1c-1995 (“POSIX.1”). 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. Subse‐
quent 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 pos‐
sible. getpwent() makes no attempt to suppress duplicate information if
multiple sources are specified in nsswitch.conf(5).
BSD April 30, 2008 BSD
