|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
Another version of this page is provided by the shadow-utils project
|
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | FILES | ATTRIBUTES | VERSIONS | STANDARDS | SEE ALSO | COLOPHON |
|
|
|
getspnam(3) Library Functions 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
Standard C library (libc, -lc)
/* 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 *stream);
struct spwd *sgetspent(const char *s);
int putspent(const struct spwd *p, FILE *stream);
int lckpwdf(void);
int ulckpwdf(void);
/* GNU extension */
#include <shadow.h>
int getspent_r(size_t size;
struct spwd *spbuf,
char buf[size], size_t size, struct spwd **spbufp);
int getspnam_r(size_t size;
const char *name, struct spwd *spbuf,
char buf[size], size_t size, struct spwd **spbufp);
int fgetspent_r(size_t size;
FILE *stream, struct spwd *spbuf,
char buf[size], size_t size, struct spwd **spbufp);
int sgetspent_r(size_t size;
const char *s, struct spwd *spbuf,
char buf[size], size_t size, struct spwd **spbufp);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
getspent_r(), getspnam_r(), fgetspent_r(), sgetspent_r():
Since glibc 2.19:
_DEFAULT_SOURCE
glibc 2.19 and earlier:
_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
stream. 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.
Reentrant versions
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
size. 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.
Structure
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, with errno set to indicate the error.
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.
EACCES The caller does not have permission to access the shadow
password file.
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.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────────┬───────────────┬────────────────────────────────┐
│ Interface │ Attribute │ Value │
├───────────────┼───────────────┼────────────────────────────────┤
│ getspnam() │ Thread safety │ MT-Unsafe race:getspnam locale │
├───────────────┼───────────────┼────────────────────────────────┤
│ getspent() │ Thread safety │ MT-Unsafe race:getspent │
│ │ │ race:spentbuf locale │
├───────────────┼───────────────┼────────────────────────────────┤
│ setspent(), │ Thread safety │ MT-Unsafe race:getspent locale │
│ endspent(), │ │ │
│ getspent_r() │ │ │
├───────────────┼───────────────┼────────────────────────────────┤
│ fgetspent() │ Thread safety │ MT-Unsafe race:fgetspent │
├───────────────┼───────────────┼────────────────────────────────┤
│ sgetspent() │ Thread safety │ MT-Unsafe race:sgetspent │
├───────────────┼───────────────┼────────────────────────────────┤
│ putspent(), │ Thread safety │ MT-Safe locale │
│ getspnam_r(), │ │ │
│ sgetspent_r() │ │ │
├───────────────┼───────────────┼────────────────────────────────┤
│ lckpwdf(), │ Thread safety │ MT-Safe │
│ ulckpwdf(), │ │ │
│ fgetspent_r() │ │ │
└───────────────┴───────────────┴────────────────────────────────┘
In the above table, getspent in race:getspent signifies that if
any of the functions setspent(), getspent(), getspent_r(), or
endspent() are used in parallel in different threads of a program,
then data races could occur.
Many other systems provide a similar API.
None.
getgrnam(3), getpwnam(3), getpwnam_r(3), shadow(5)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.15 2025-06-28 getspnam(3)
Pages that refer to this page: getent(1), getpwnam(3), setaliasent(3), nsswitch.conf(5), nscd(8)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|