setspent(3)



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

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

SYNOPSIS
       /* 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
       Long ago it was considered safe to have encrypted passwords openly vis-
       ible 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 pass-
       word 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 initial-
       ized 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 simulta-
       neous  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 simi-
       larly 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
       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
       EACCES The caller does not have permission to access the  shadow  pass-
              word file.

       ERANGE Supplied buffer is too small.

FILES
       /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
       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.

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

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

COLOPHON
       This  page  is  part of release 4.16 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                               2017-09-15                       GETSPNAM(3)

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