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man:ulckpwdf

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).
     allbox; lbw13 lb lbw30 l l l.  Interface Attribute Value T{  getspnam()
     T}   Thread  safety  T{ MT-Unsafe race:getspnam locale T} T{ getspent()
     T}   Thread safety  T{ MT-Unsafe race:getspent
     race:spentbuf locale T} T{ setspent(),
     endspent(),
     getspent_r() T}   Thread safety  T{ MT-Unsafe race:getspent  locale  T}
     T{  fgetspent()  T}   Thread  safety  MT-Unsafe race:fgetspent T{ sget-
     spent() T}   Thread safety  MT-Unsafe race:sgetspent T{ putspent(),
     getspnam_r(),
     sgetspent_r() T}   Thread safety  MT-Safe locale T{ lckpwdf(),
     ulckpwdf(),
     fgetspent_r() T}   Thread safety  MT-Safe
     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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