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.\" Copyright (c) 2003 Andries Brouwer (aeb@cwi.nl) and
.\" Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.\"
.\" Distributed under GPL
.\"
.TH GETSPNAM 3 2003-11-15 "Shadow" "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 */
.br
.B #include <shadow.h>
.sp
.BI "struct spwd *getspnam(const char *" name );
.sp
.B struct spwd *getspent(void);
.sp
.B void setspent(void);
.sp
.B void endspent(void);
.sp
.BI "struct spwd *fgetspent(FILE *" fp );
.sp
.BI "struct spwd *sgetspent(const char *" s );
.sp
.BI "int putspent(struct spwd *" p ", FILE *" fp );
.sp
.B int lckpwdf(void);
.sp
.B int ulckpwdf(void);
.sp
/* GNU extension */
.br
.BR "#define _SVID_SOURCE" " /* or _BSD_SOURCE */
.br
.B #include <shadow.h>
.sp
.BI "int getspent_r(struct spwd *" spbuf ,
.br
.BI " char *" buf ", size_t " buflen ", struct spwd **" spbufp );
.sp
.BI "int getspnam_r(const char *" name ", struct spwd *" spbuf ,
.br
.BI " char *" buf ", size_t " buflen ", struct spwd **" spbufp );
.sp
.BI "int fgetspent_r(FILE *" fp ", struct spwd *" spbuf ,
.br
.BI " char *" buf ", size_t " buflen ", struct spwd **" spbufp );
.sp
.BI "int sgetspent_r(const char *" s ", struct spwd *" spbuf ,
.br
.BI " char *" buf ", size_t " buflen ", struct spwd **" spbufp );
.sp
.fi
.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
.IR /etc/shadow ,
readable only by root.
.LP
The access routines described below resemble those for
.IR /etc/passwd .
This shadow password setup has been superseded by PAM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.
.LP
The
.B getspnam()
function returns a pointer to a structure containing
the broken out fields of a line from
.I /etc/shadow
for the entry that matches the user name
.IR name .
.LP
The
.B getspent()
function returns a pointer to the next entry in the shadow password file.
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
.LP
The
.B fgetspent()
function is similar to
.B getspent()
but uses the supplied stream instead of the one implicitly opened by
.BR setspent() .
.LP
The
.B sgetspent()
function parses the supplied string
.I s
into a struct spwd.
.LP
The
.B putspent()
function writes the contents of the supplied struct spwd
.RI * p
as a text line in the shadow password file format to the stream
.IR fp .
String entries with value NULL and numerical entries with value \-1
are written as an empty string.
.LP
The
.B lckpwdf()
function is intended to protect against multiple access of the shadow
password database. It tries to acquire a lock, and returns 0 on success,
\-1 on failure (lock not obtained within 15 seconds).
The
.B ulckpwdf()
function releases the lock again.
Note that there is no protection against direct access of the shadow
password file. Only programs that use
.B lckpwdf()
will notice the lock.
.LP
These were the routines 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" routines for the password file, glibc
also has reentrant versions here.
The
.B getspnam_r()
function is like
.B getspnam()
but stores the retrieved shadow passwd structure in the space pointed to by
.IR spbuf .
This shadow passwd 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
.RI * spbufp .
.LP
The functions
.BR getspent_r() ,
.BR fgetspent_r() ,
and
.BR sgetspent_r()
are completely analogous.
.LP
Some non-glibc systems also have functions with these names,
often with different prototypes.
.\" SUN doesn't have sgetspent_r()
.SS Structure
The shadow passwd structure is defined in \fI<shadow.h>\fP as follows:
.sp
.nf
struct spwd {
char *sp_namp; /* Login name */
char *sp_pwdp; /* Encrypted password */
long sp_lstchg; /* Date of last change */
long sp_min; /* Min #days between changes */
long sp_max; /* Max #days between changes */
long sp_warn; /* #days before pwd expires
to warn user to change it */
long sp_inact; /* #days after pwd expires
until account is disabled */
long sp_expire; /* #days since 1970-01-01
until account is disabled */
unsigned long sp_flag; /* Reserved */
};
.fi
.SH "RETURN VALUE"
Routines return NULL if no more entries are available or if an
error occurs during processing.
Routines which have \fBint\fR as the return value return 0 for
success and -1 for failure.
.LP
For the non-reentrant functions, the return value may point to static area,
and may be overwritten by subsequent calls to these functions.
.LP
The reentrant functions return zero on success.
In case of error, an error value is returned.
.SH ERRORS
.TP
.B ERANGE
Supplied buffer is too small.
.SH FILES
.TP
.I /etc/shadow
shadow password database file
.TP
.I /etc/.pwd.lock
lock file
.LP
The include file
.I <paths.h>
defines the constant _PATH_SHADOW to the pathname of the shadow
password file.
.SH "CONFORMING TO"
.SH "SEE ALSO"
.BR getgrnam (3),
.BR getpwnam (3),
.BR getpwnam_r (3),
.BR shadow (5)
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