minix/lib/libc/gen/getpwent.3

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.\"     @(#)getpwent.3	8.2 (Berkeley) 12/11/93
.\"
.Dd April 30, 2008
.Dt GETPWENT 3
.Os
.Sh NAME
.Nm getpwent ,
.Nm getpwent_r ,
.Nm getpwnam ,
.Nm getpwnam_r ,
.Nm getpwuid ,
.Nm getpwuid_r ,
.Nm setpassent ,
.Nm setpwent ,
.Nm endpwent
.Nd password database operations
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In pwd.h
.Ft struct passwd *
.Fn getpwent void
.Ft int
.Fo getpwent_r
.Fa "struct passwd *pw"
.Fa "char *buffer"
.Fa "size_t buflen"
.Fa "struct passwd **result"
.Fc
.Ft struct passwd *
.Fn getpwnam "const char *name"
.Ft int
.Fo getpwnam_r
.Fa "const char *name"
.Fa "struct passwd *pw"
.Fa "char *buffer"
.Fa "size_t buflen"
.Fa "struct passwd **result"
.Fc
.Ft struct passwd *
.Fn getpwuid "uid_t uid"
.Ft int
.Fo getpwuid_r
.Fa "uid_t uid"
.Fa "struct passwd *pw"
.Fa "char *buffer"
.Fa "size_t buflen"
.Fa "struct passwd **result"
.Fc
.Ft int
.Fn setpassent "int stayopen"
.Ft void
.Fn setpwent void
.Ft void
.Fn endpwent void
.Sh DESCRIPTION
These functions
operate on the password database
which is described
in
.Xr passwd 5 .
Each entry in the database is defined by the structure
.Ar passwd
found in the include
file
.In pwd.h :
.Bd -literal -offset indent
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 */
};
.Ed
.Pp
The functions
.Fn getpwnam
and
.Fn getpwuid
search the password database for the given user name pointed to by
.Ar name
or user id pointed to by
.Ar uid
respectively, always returning the first one encountered.
Identical user names or user ids may result in undefined behavior.
.Pp
The
.Fn getpwent
function
sequentially reads the password database and is intended for programs
that wish to process the complete list of users.
.Pp
The functions
.Fn getpwnam_r ,
.Fn getpwuid_r ,
and
.Fn getpwent_r
act like their non re-entrant counterparts, updating the contents of
.Ar pw
and storing a pointer to that in
.Ar result ,
and returning
.Dv 0 .
Storage used by
.Ar pw
is allocated from
.Ar buffer ,
which is
.Ar buflen
bytes in size.
If the requested entry cannot be found,
.Ar result
will point to
.Dv NULL
and
.Dv 0
will be returned.
If an error occurs,
a non-zero error number will be returned and
.Ar result
will point to
.Dv NULL .
Calling
.Fn getpwent_r
from multiple threads will result in each thread reading a disjoint portion
of the password database.
.Pp
The
.Fn setpassent
function
accomplishes two purposes.
First, it causes
.Fn getpwent
to
.Dq rewind
to the beginning of the database.
Additionally, if
.Fa 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
.Fn getpwent
as it doesn't close its file descriptors by default.)
.Pp
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.
.Pp
The
.Fn setpwent
function
is equivalent to
.Fn setpassent
with an argument of zero.
.Pp
The
.Fn endpwent
function
closes any open files.
.Pp
These functions have been written to
.Dq 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
.Ql * .
.Sh RETURN VALUES
The functions
.Fn getpwent ,
.Fn getpwnam ,
and
.Fn getpwuid ,
return a valid pointer to a passwd structure on success
and a
.Dv NULL
pointer if the entry was not found or an error occured.
If an error occured, the global variable
.Dv errno
is set to indicate the nature of the failure.
The
.Fn setpassent
function returns 0 on failure, setting the global variable
.Dv errno
to indicate the nature of the failure, and 1 on success.
The
.Fn endpwent
and
.Fn setpwent
functions
have no return value.
The functions
.Fn getpwnam_r ,
.Fn getpwuid_r ,
and
.Fn getpwent_r
return
.Dv 0
on success or entry not found, and non-zero on failure, setting the global
variable
.Dv errno
to indicate the nature of the failure.
.Sh FILES
.Bl -tag -width /etc/master.passwd -compact
.It Pa /etc/pwd.db
The insecure password database file
.It Pa /etc/spwd.db
The secure password database file
.It Pa /etc/master.passwd
The current password file
.It Pa /etc/passwd
A Version 7 format password file
.El
.Sh COMPATIBILITY
The historic function
.Fn setpwfile
which allowed the specification of alternative password databases,
has been deprecated and is no longer available.
.Sh ERRORS
The following error codes may be set in
.Va errno
for
.Nm getpwent ,
.Nm getpwent_r ,
.Nm getpwnam ,
.Nm getpwnam_r ,
.Nm getpwuid ,
.Nm getpwuid_r ,
and
.Nm setpassent :
.Bl -tag -width Er
.It Bq Er EINTR
A signal was caught during the database search.
.It Bq Er EIO
An I/O error has occurred.
.It Bq Er EMFILE
The limit on open files for this process has been reached.
.It Bq Er ENFILE
The system limit on open files has been reached.
.El
.Pp
The following error code may be set in
.Va errno
for
.Nm getpwent_r ,
.Nm getpwnam_r ,
and
.Nm getpwuid_r :
.Bl -tag -width Er
.It Bq Er ERANGE
The resulting
.Ft struct passwd
does not fit in the space defined by
.Dv buffer
and
.Dv buflen
.El
.Pp
Other
.Dv errno
values may be set depending on the specific database backends.
.Sh SEE ALSO
.Xr getlogin 2 ,
.Xr getgrent 3 ,
.Xr nsswitch.conf 5 ,
.Xr passwd 5 ,
.Xr passwd.conf 5 ,
.Xr pwd_mkdb 8 ,
.Xr vipw 8
.Sh STANDARDS
The
.Fn getpwnam
and
.Fn getpwuid ,
functions conform to
.St -p1003.1-90 .
The
.Fn getpwnam_r
and
.Fn getpwuid_r
functions conform to
.St -p1003.1c-95 .
The
.Fn endpwent ,
.Fn getpwent ,
and
.Fn setpwent
functions conform to
.St -xpg4.2
and
.St -p1003.1-2004
(XSI extension).
.Sh HISTORY
The
.Nm getpwent ,
.Nm getpwnam ,
.Nm getpwuid ,
.Nm setpwent ,
and
.Nm endpwent
functions appeared in
.At v7 .
The
.Nm setpassent
function appeared in
.Bx 4.3 Reno .
The functions
.Fn getpwnam_r
and
.Fn getpwuid_r
appeared in
.Nx 3.0 .
.Sh BUGS
The functions
.Fn getpwent ,
.Fn getpwnam ,
and
.Fn 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.
.Pp
The functions
.Fn getpwent ,
.Fn endpwent ,
.Fn setpassent ,
and
.Fn setpwent
are fairly useless in a networked environment and should be
avoided, if possible.
.Fn getpwent
makes no attempt to suppress duplicate information if multiple
sources are specified in
.Xr nsswitch.conf 5 .