GETSPNAM(3)               (2017-09-15)                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

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     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 pass-
          word file /etc/shadow, NIS,  and  LDAP),  readable  only  by
          root.

          The functions described below resemble those for the  tradi-
          tional   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 deallo-
          cated.

          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 numeri-
          cal entries with value -1 are written as an empty string.

          The lckpwdf() function is intended to protect against multi-
          ple  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  data-
          base,  glibc  also  has  reentrant  functions for the shadow
          password  database.   The  getspnam_r()  function  is   like

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          getspnam()  but  stores the retrieved shadow password struc-
          ture 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 process-
          ing.  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

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               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).     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{ sgetspent() 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  differ-
          ent 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 5.10  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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