NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | FILES | ATTRIBUTES | CONFORMING TO | SEE ALSO | COLOPHON

GETSPNAM(3)               Linux Programmer's Manual              GETSPNAM(3)

NAME         top

       getspnam, getspnam_r, getspent, getspent_r, setspent, endspent, fget‐
       spent, fgetspent_r, sgetspent, sgetspent_r, putspent, lckpwdf, ulckp‐
       wdf - get shadow password file entry

SYNOPSIS         top

       /* 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(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 *stream, 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():
           Since glibc 2.19:
               _DEFAULT_SOURCE
           Glibc 2.19 and earlier:
               _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       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 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.

   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 */
           };

RETURN VALUE         top

       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 cause of 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.

ERRORS         top

       EACCES The caller does not have permission to access the shadow
              password file.

       ERANGE Supplied buffer is too small.

FILES         top

       /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.

ATTRIBUTES         top

       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(3), getspent(3), getspent_r(3), or
       endspent(3) are used in parallel in different threads of a program,
       then data races could occur.

CONFORMING TO         top

       The shadow password database and its associated API are not specified
       in POSIX.1.  However, many other systems provide a similar API.

SEE ALSO         top

       getgrnam(3), getpwnam(3), getpwnam_r(3), shadow(5)

COLOPHON         top

       This page is part of release 4.07 of the Linux 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/.

GNU                              2016-03-15                      GETSPNAM(3)