shadow, getspnam − encrypted password file routines

     #include <shadow.h>

     struct spwd *getspent();

     struct spwd *getspnam(char *name);

     void setspent();

     void endspent();

     struct spwd *fgetspent(FILE *fp);

     struct spwd *sgetspent(char *cp);

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

     int lckpwdf();

     int ulckpwdf();

     shadow manipulates the contents of the shadow password
file, /etc/shadow. The structure in the #include file is:

     struct spwd {
           char          *sp_namp; /* user login name */
           char          *sp_pwdp; /* encrypted password */
           long int      sp_lstchg; /* last password change */
           long int      sp_min; /* days until change allowed. */
           long int      sp_max; /* days before change required */
           long int      sp_warn; /* days warning for expiration */
           long int      sp_inact; /* days before account inactive */
           long int      sp_expire; /* date when account expires */
           unsigned long int  sp_flag; /* reserved for future use */

     The meanings of each field are:

 •   sp_namp − pointer to null−terminated user name

 •   sp_pwdp − pointer to null−terminated password

 •   sp_lstchg − days since Jan 1, 1970 password was last

 •   sp_min − days before which password may not be changed

 •   sp_max − days after which password must be changed


 •   sp_warn − days before password is to expire that user
     is warned of pending password expiration

 •   sp_inact − days after password expires that account is
     considered inactive and disabled

 •   sp_expire − days since Jan 1, 1970 when account will be

 •   sp_flag − reserved for future use

     getspent, getspname, fgetspent, and sgetspent each
return a pointer to a struct spwd.  getspent returns the
next entry from the file, and fgetspent returns the next
entry from the given stream, which is assumed to be a file
of the proper format.  sgetspent returns a pointer to a
struct spwd using the provided string as input.  getspnam
searches from the current position in the file for an entry
matching name.

     setspent and endspent may be used to begin and end,
respectively, access to the shadow password file.

     The lckpwdf and ulckpwdf routines should be used to
insure exclusive access to the /etc/shadow file.  lckpwdf
attempts to acquire a lock using pw_lock for up to 15
seconds. It continues by attempting to acquire a second lock
using spw_lock for the remainder of the initial 15 seconds.
Should either attempt fail after a total of 15 seconds,
lckpwdf returns −1. When both locks are acquired 0 is

     Routines return NULL if no more entries are available
or if an error occurs during processing. Routines which have
int as the return value return 0 for success and −1 for

     These routines may only be used by the superuser as
access to the shadow password file is restricted.

     Secure user account information.


     getpwent(3), shadow(5).