| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | FILES | CONFORMING TO | SEE ALSO | COLOPHON | The Linux Programming Interface |
GETSPNAM(3) Linux Programmer's Manual GETSPNAM(3)
getspnam, getspnam_r, getspent, getspent_r, setspent, endspent, fgetspent,
fgetspent_r, sgetspent, sgetspent_r, putspent, lckpwdf, ulckpwdf - get shadow
password file entry
/* General shadow password file API */
#include <shadow.h>
struct spwd *getspnam(const char *name);
struct spwd *getspent(void);
void setspent(void);
void endspent(void);
struct spwd *fgetspent(FILE *fp);
struct spwd *sgetspent(const char *s);
int putspent(struct spwd *p, FILE *fp);
int lckpwdf(void);
int ulckpwdf(void);
/* GNU extension */
#include <shadow.h>
int getspent_r(struct spwd *spbuf,
char *buf, size_t buflen, struct spwd **spbufp);
int getspnam_r(const char *name, struct spwd *spbuf,
char *buf, size_t buflen, struct spwd **spbufp);
int fgetspent_r(FILE *fp, struct spwd *spbuf,
char *buf, size_t buflen, struct spwd **spbufp);
int sgetspent_r(const char *s, struct spwd *spbuf,
char *buf, size_t buflen, struct spwd **spbufp);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
getspent_r(), getspnam_r(), fgetspent_r(), sgetspent_r():
_BSD_SOURCE || _SVID_SOURCE
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 /etc/shadow, NIS, and
LDAP), readable only by root.
The functions described below resemble those for the traditional password
database (e.g., see getpwnam(3) and getpwent(3)).
The 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 name.
The getspent() function returns a pointer to the next entry in the shadow
password database. The position in the input stream is initialized by
setspent(). When done reading, the program may call endspent() so that
resources can be deallocated.
The fgetspent() function is similar to getspent() but uses the supplied stream
instead of the one implicitly opened by setspent().
The sgetspent() function parses the supplied string s into a struct spwd.
The putspent() function writes the contents of the supplied struct spwd *p as
a text line in the shadow password file format to the stream fp. String
entries with value NULL and numerical entries with value -1 are written as an
empty string.
The 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 ulckpwdf() function releases the lock again. Note that there is no
protection against direct access of the shadow password file. Only programs
that use lckpwdf() will notice the lock.
These were the functions that formed the original shadow API. They are widely
available.
Analogous to the reentrant functions for the password database, glibc also has
reentrant functions for the shadow password database. The getspnam_r()
function is like getspnam() but stores the retrieved shadow password structure
in the space pointed to by spbuf. This shadow password structure contains
pointers to strings, and these strings are stored in the buffer buf of size
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 *spbufp.
The functions getspent_r(), fgetspent_r(), and sgetspent_r() are similarly
analogous to their nonreentrant counterparts.
Some non-glibc systems also have functions with these names, often with
different prototypes.
The shadow password structure is defined in <shadow.h> as follows:
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 */
};
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
int as the return value return 0 for success and -1 for failure.
For the nonreentrant functions, the return value may point to static area, and
may be overwritten by subsequent calls to these functions.
The reentrant functions return zero on success. In case of error, an error
number is returned.
ERANGE Supplied buffer is too small.
/etc/shadow
local shadow password database file
/etc/.pwd.lock
lock file
The include file <paths.h> defines the constant _PATH_SHADOW to the pathname
of the shadow password file.
The shadow password database and its associated API are not specified in
POSIX.1-2001. However, many other systems provide a similar API.
getgrnam(3), getpwnam(3), getpwnam_r(3), shadow(5)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2010-02-25 GETSPNAM(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface