libc/gen/getpwent.3

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.\"     @(#)getpwent.3	8.2 (Berkeley) 12/11/93
.\"
.Dd April 25, 1999
.Dt GETPWENT 3
.Os
.Sh NAME
.Nm getpwent ,
.Nm getpwnam ,
.Nm getpwuid ,
.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 struct passwd *
.Fn getpwnam "const char *login"
.Ft struct passwd *
.Fn getpwuid "uid_t uid"
.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 file
which is described
in
.Xr passwd 5 .
Each entry in the database is defined by the structure
.Ar passwd
found in the include
file
.Aq Pa 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 access class */
	char	*pw_gecos;	/* Honeywell login info */
	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 login name or user uid,
respectively, always returning the first one encountered.
.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
.Fn setpassent
function
accomplishes two purposes.
First, it causes
.Fn getpwent
to ``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open as the database will become out of date if it is updated while the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 ``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 null pointer if end-of-file is reached or an error occurs.
The
.Fn setpassent
function returns 0 on failure and 1 on success.
The
.Fn endpwent
and
.Fn setpwent
functions
have no return value.
.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 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 .
.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 .
.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
.Sh COMPATIBILITY
The historic function
.Fn setpwfile
which allowed the specification of alternative password databases,
has been deprecated and is no longer available.