getspnam(3)

NAME

   getspnam,   getspnam_r,   getspent,   getspent_r,  setspent,  endspent,
   fgetspent,  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
   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

   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
          password 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(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

   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 4.09 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/.

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