ulckpwdf man page on Hurd

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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 *fp);

       struct spwd *sgetspent(const char *s);

       int putspent(struct spwd *p, FILE *fp);

       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 *fp, 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():
	   _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 the stream  fp.
       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.

CONFORMING TO
       The shadow password database and its associated API are	not  specified
       in POSIX.1-2001.	 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 3.55 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU				  2013-04-19			   GETSPNAM(3)
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