getspnam(3) — Linux manual page


getspnam(3)             Library Functions Manual             getspnam(3)

NAME         top

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

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       /* 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[.buflen], size_t buflen, struct spwd **spbufp);
       int getspnam_r(const char *name, struct spwd *spbuf,
                      char buf[.buflen], size_t buflen, struct spwd **spbufp);

       int fgetspent_r(FILE *stream, struct spwd *spbuf,
                      char buf[.buflen], size_t buflen, struct spwd **spbufp);
       int sgetspent_r(const char *s, struct spwd *spbuf,
                      char buf[.buflen], size_t buflen, struct spwd **spbufp);

   Feature Test Macro Requirements for glibc (see

       getspent_r(), getspnam_r(), fgetspent_r(), sgetspent_r():
           Since glibc 2.19:
           glibc 2.19 and earlier:
               _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       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

       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.

       The shadow password structure is defined in <shadow.h> as

           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         top

       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 error.

       For the nonreentrant functions, the return value may point to
       static area, and may be overwritten by subsequent calls to these

       The reentrant functions return zero on success.  In case of
       error, an error number is returned.

ERRORS         top

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

       ERANGE Supplied buffer is too small.

FILES         top

              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.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ 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       │
       │ endspent(),   │               │ locale                        │
       │ 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(), getspent(), getspent_r(), or
       endspent() are used in parallel in different threads of a
       program, then data races could occur.

VERSIONS         top

       Many other systems provide a similar API.

STANDARDS         top


SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                    getspnam(3)

Pages that refer to this page: getent(1)getpwnam(3)setaliasent(3)nsswitch.conf(5)nscd(8)