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


   /* 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:
       Glibc 2.19 and earlier:
           _BSD_SOURCE || _SVID_SOURCE


   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

   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

   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

   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.

   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 */


   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.


   EACCES The  caller  does  not  have  permission  to  access  the shadow
          password file.

   ERANGE Supplied buffer is too small.


          local shadow password database file

          lock file

   The include file <paths.h> defines the  constant  _PATH_SHADOW  to  the
   pathname of the shadow password file.


   For   an   explanation   of   the  terms  used  in  this  section,  see

   │InterfaceAttributeValue                          │
   │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.


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


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


   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


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.