xref: /freebsd/lib/libc/gen/getpwent.3 (revision dc36d6f9bb1753f3808552f3afd30eda9a7b206a)

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.Dd November 28, 2022
.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
.Fn getpwent_r "struct passwd *pwd" "char *buffer" "size_t bufsize" "struct passwd **result"
.Ft struct passwd *
.Fn getpwnam "const char *login"
.Ft int
.Fn getpwnam_r "const char *name" "struct passwd *pwd" "char *buffer" "size_t bufsize" "struct passwd **result"
.Ft struct passwd *
.Fn getpwuid "uid_t uid"
.Ft int
.Fn getpwuid_r "uid_t uid" "struct passwd *pwd" "char *buffer" "size_t bufsize" "struct passwd **result"
.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
.Vt 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 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 */
};
.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 functions
.Fn getpwent_r ,
.Fn getpwnam_r ,
and
.Fn getpwuid_r
are thread-safe versions of
.Fn getpwent ,
.Fn getpwnam ,
and
.Fn getpwuid ,
respectively.
The caller must provide storage for the results of the search in
the
.Fa pwd ,
.Fa buffer ,
.Fa bufsize ,
and
.Fa result
arguments.
When these functions are successful, the
.Fa pwd
argument will be filled-in, and a pointer to that argument will be
stored in
.Fa result .
If an entry is not found or an error occurs,
.Fa result
will be set to
.Dv NULL .
.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 routines.
(This latter functionality is unnecessary for
.Fn getpwent
as it does not 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 identical to
.Fn setpassent
with an argument of zero.
.Pp
The
.Fn endpwent
function
closes any open files.
.Pp
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
.Ql * .
.Sh RETURN VALUES
The functions
.Fn getpwent ,
.Fn getpwnam ,
and
.Fn getpwuid
return a valid pointer to a passwd structure on success
or
.Dv NULL
if the entry is not found or if an error occurs.
If an error does occur,
.Va errno
will be set.
Note that programs must explicitly set
.Va errno
to zero before calling any of these functions if they need to
distinguish between a non-existent entry and an error.
The functions
.Fn getpwent_r ,
.Fn getpwnam_r ,
and
.Fn getpwuid_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
.Fa result
is
.Dv NULL
and the return value is 0, no matching entry exists.)
.Pp
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 COMPATIBILITY
The historic function
.Xr setpwfile 3 ,
which allowed the specification of alternate password databases,
has been deprecated and is no longer available.
.Sh ERRORS
These routines may fail for any of the errors specified in
.Xr open 2 ,
.Xr dbopen 3 ,
.Xr socket 2 ,
and
.Xr connect 2 ,
in addition to the following:
.Bl -tag -width Er
.It Bq Er ERANGE
The buffer specified by the
.Fa buffer
and
.Fa bufsize
arguments was insufficiently sized to store the result.
The caller should retry with a larger buffer.
.El
.Sh SEE ALSO
.Xr getlogin 2 ,
.Xr getgrent 3 ,
.Xr nsswitch.conf 5 ,
.Xr passwd 5 ,
.Xr pwd_mkdb 8 ,
.Xr vipw 8 ,
.Xr yp 8
.Sh STANDARDS
The
.Fn getpwent ,
.Fn getpwnam ,
.Fn getpwnam_r ,
.Fn getpwuid ,
.Fn getpwuid_r ,
.Fn setpwent ,
and
.Fn endpwent
functions conform to
.St -p1003.1-96 .
.Sh HISTORY
The
.Fn getpwent ,
.Fn getpwnam ,
.Fn getpwuid ,
.Fn setpwent ,
and
.Fn endpwent
functions appeared in
.At v7 .
The
.Fn setpassent
function appeared in
.Bx 4.3 Reno .
The
.Fn getpwent_r ,
.Fn getpwnam_r ,
and
.Fn getpwuid_r
functions appeared in
.Fx 5.1 .
.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
the same function
will modify the same object.
.Pp
The functions
.Fn getpwent ,
.Fn getpwent_r ,
.Fn endpwent ,
.Fn setpassent ,
and
.Fn setpwent
are fairly useless in a networked environment and should be
avoided, if possible.
The
.Fn getpwent
and
.Fn getpwent_r
functions
make no attempt to suppress duplicate information if multiple
sources are specified in
.Xr nsswitch.conf 5 .