.\" Copyright (c) 2003 Andries Brouwer (aeb@cwi.nl) and
.\" Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.\"
.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
.\" Distributed under GPL
.\" %%%LICENSE_END
.\"
.TH GETSPNAM 3  2017-09-15 "GNU" "Linux Programmer's Manual"
.SH NAME
getspnam, getspnam_r, getspent, getspent_r, setspent, endspent,
fgetspent, fgetspent_r, sgetspent, sgetspent_r, putspent,
lckpwdf, ulckpwdf \- get shadow password file entry
.SH SYNOPSIS
.nf
/* General shadow password file API */
.B #include <shadow.h>
.PP
.BI "struct spwd *getspnam(const char *" name );
.PP
.B struct spwd *getspent(void);
.PP
.B void setspent(void);
.PP
.B void endspent(void);
.PP
.BI "struct spwd *fgetspent(FILE *" stream );
.PP
.BI "struct spwd *sgetspent(const char *" s );
.PP
.BI "int putspent(const struct spwd *" p ", FILE *" stream );
.PP
.B int lckpwdf(void);
.PP
.B int ulckpwdf(void);

/* GNU extension */
.B #include <shadow.h>
.PP
.BI "int getspent_r(struct spwd *" spbuf ,
.BI "        char *" buf ", size_t " buflen ", struct spwd **" spbufp );
.PP
.BI "int getspnam_r(const char *" name ", struct spwd *" spbuf ,
.BI "        char *" buf ", size_t " buflen ", struct spwd **" spbufp );
.PP
.BI "int fgetspent_r(FILE *" stream ", struct spwd *" spbuf ,
.BI "        char *" buf ", size_t " buflen ", struct spwd **" spbufp );
.PP
.BI "int sgetspent_r(const char *" s ", struct spwd *" spbuf ,
.BI "        char *" buf ", size_t " buflen ", struct spwd **" spbufp );
.fi
.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.PP
.ad l
.BR getspent_r (),
.BR getspnam_r (),
.BR fgetspent_r (),
.BR sgetspent_r ():
    Since glibc 2.19:
        _DEFAULT_SOURCE
    Glibc 2.19 and earlier:
        _BSD_SOURCE || _SVID_SOURCE
.ad b
.SH DESCRIPTION
Long ago it was considered safe to have encrypted passwords openly
visible in the password file.
When computers got faster and people
got more security-conscious, this was no longer acceptable.
Julianne Frances Haugh implemented the shadow password suite
that keeps the encrypted passwords in
the shadow password database
(e.g., the local shadow password file
.IR /etc/shadow ,
NIS, and LDAP),
readable only by root.
.PP
The functions described below resemble those for
the traditional password database
(e.g., see
.BR getpwnam (3)
and
.BR getpwent (3)).
.\" FIXME . I've commented out the following for the
.\" moment.  The relationship between PAM and nsswitch.conf needs
.\" to be clearly documented in one place, which is pointed to by
.\" the pages for the user, group, and shadow password functions.
.\" (Jul 2005, mtk)
.\"
.\" This shadow password setup has been superseded by PAM
.\" (pluggable authentication modules), and the file
.\" .I /etc/nsswitch.conf
.\" now describes the sources to be used.
.PP
The
.BR getspnam ()
function returns a pointer to a structure containing
the broken-out fields of the record in the shadow password database
that matches the username
.IR name .
.PP
The
.BR getspent ()
function returns a pointer to the next entry in the shadow password
database.
The position in the input stream is initialized by
.BR setspent ().
When done reading, the program may call
.BR endspent ()
so that resources can be deallocated.
.\" some systems require a call of setspent() before the first getspent()
.\" glibc does not
.PP
The
.BR fgetspent ()
function is similar to
.BR getspent ()
but uses the supplied stream instead of the one implicitly opened by
.BR setspent ().
.PP
The
.BR sgetspent ()
function parses the supplied string
.I s
into a struct
.IR spwd .
.PP
The
.BR putspent ()
function writes the contents of the supplied struct
.I spwd
.I *p
as a text line in the shadow password file format to
.IR stream .
String entries with value NULL and numerical entries with value \-1
are written as an empty string.
.PP
The
.BR lckpwdf ()
function is intended to protect against multiple simultaneous accesses
of the shadow password database.
It tries to acquire a lock, and returns 0 on success,
or \-1 on failure (lock not obtained within 15 seconds).
The
.BR ulckpwdf ()
function releases the lock again.
Note that there is no protection against direct access of the shadow
password file.
Only programs that use
.BR lckpwdf ()
will notice the lock.
.PP
These were the functions that formed the original shadow API.
They are widely available.
.\" Also in libc5
.\" SUN doesn't have sgetspent()
.SS Reentrant versions
Analogous to the reentrant functions for the password database, glibc
also has reentrant functions for the shadow password database.
The
.BR getspnam_r ()
function is like
.BR getspnam ()
but stores the retrieved shadow password structure in the space pointed to by
.IR spbuf .
This shadow password structure contains pointers to strings, and these strings
are stored in the buffer
.I buf
of size
.IR buflen .
A pointer to the result (in case of success) or NULL (in case no entry
was found or an error occurred) is stored in
.IR *spbufp .
.PP
The functions
.BR getspent_r (),
.BR fgetspent_r (),
and
.BR sgetspent_r ()
are similarly analogous to their nonreentrant counterparts.
.PP
Some non-glibc systems also have functions with these names,
often with different prototypes.
.\" SUN doesn't have sgetspent_r()
.SS Structure
The shadow password structure is defined in \fI<shadow.h>\fP as follows:
.PP
.in +4n
.EX
struct spwd {
    char *sp_namp;     /* Login name */
    char *sp_pwdp;     /* Encrypted password */
    long  sp_lstchg;   /* Date of last change
                          (measured in days since
                          1970-01-01 00:00:00 +0000 (UTC)) */
    long  sp_min;      /* Min # of days between changes */
    long  sp_max;      /* Max # of days between changes */
    long  sp_warn;     /* # of days before password expires
                          to warn user to change it */
    long  sp_inact;    /* # of days after password expires
                          until account is disabled */
    long  sp_expire;   /* Date when account expires
                          (measured in days since
                          1970-01-01 00:00:00 +0000 (UTC)) */
    unsigned long sp_flag;  /* Reserved */
};
.EE
.in
.SH RETURN VALUE
The functions that return a pointer return NULL if no more entries
are available or if an error occurs during processing.
The functions which have \fIint\fP as the return value return 0 for
success and \-1 for failure, with
.I errno
set to indicate the cause of the error.
.PP
For the nonreentrant functions, the return value may point to static area,
and may be overwritten by subsequent calls to these functions.
.PP
The reentrant functions return zero on success.
In case of error, an error number is returned.
.SH ERRORS
.TP
.B EACCES
The caller does not have permission to access the shadow password file.
.TP
.B ERANGE
Supplied buffer is too small.
.SH FILES
.TP
.I /etc/shadow
local shadow password database file
.TP
.I /etc/.pwd.lock
lock file
.PP
The include file
.I <paths.h>
defines the constant
.B _PATH_SHADOW
to the pathname of the shadow password file.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw13 lb lbw30
l l l.
Interface	Attribute	Value
T{
.BR getspnam ()
T}	Thread safety	T{
MT-Unsafe race:getspnam locale
T}
T{
.BR getspent ()
T}	Thread safety	T{
MT-Unsafe race:getspent
.br
race:spentbuf locale
T}
T{
.BR setspent (),
.br
.BR endspent (),
.br
.BR getspent_r ()
T}	Thread safety	T{
MT-Unsafe race:getspent locale
T}
T{
.BR fgetspent ()
T}	Thread safety	MT-Unsafe race:fgetspent
T{
.BR sgetspent ()
T}	Thread safety	MT-Unsafe race:sgetspent
T{
.BR putspent (),
.br
.BR getspnam_r (),
.br
.BR sgetspent_r ()
T}	Thread safety	MT-Safe locale
T{
.BR lckpwdf (),
.br
.BR ulckpwdf (),
.br
.BR fgetspent_r ()
T}	Thread safety	MT-Safe
.TE
.sp 1
In the above table,
.I getspent
in
.I race:getspent
signifies that if any of the functions
.BR setspent (),
.BR getspent (),
.BR getspent_r (),
or
.BR endspent ()
are used in parallel in different threads of a program,
then data races could occur.
.SH CONFORMING TO
The shadow password database and its associated API are
not specified in POSIX.1.
However, many other systems provide a similar API.
.SH SEE ALSO
.BR getgrnam (3),
.BR getpwnam (3),
.BR getpwnam_r (3),
.BR shadow (5)
.SH COLOPHON
This page is part of release 4.16 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.