#include <sys/types.h>
#include <pwd.h>

struct passwd *getpwent(void);
struct passwd *getpwnam(char *login);
struct passwd *getpwuid(uid_t uid);
int setpassent(int stayopen);
int setpwent(void);
void endpwent(void);

struct passwd {
 char *pw_name; /* user name */
 char *pw_passwd; /* encrypted password */
 uid_t pw_uid; /* user uid */
 gid_t pw_gid; /* user gid */
 time_t pw_change; /* password change time */
 char *pw_class; /* user access class */
 char *pw_gecos; /* Honeywell login info */
 char *pw_dir; /* home directory */
 char *pw_shell; /* default shell */
 time_t pw_expire; /* account expiration */
};

These fields are more completely described in passwd (5).

Getpwnam and getpwuid search the password database for a matching user name or user uid, respectively, always returning the first one encountered.

Getpwent sequentially reads the password database and is intended for programs that wish to process the complete list of users.

Setpassent accomplishes two purposes. First, it causes getpwent to ``rewind'' to the beginning of the database. Additionally, if stayopen is non-zero, file descriptors are left open, significantly speeding up subsequent accesses for all of the routines. (This latter functionality is unnecessary for getpwent as it doesn't close its file descriptors by default.)

It is dangerous for long-running programs to keep the file descriptors open the database will become out of date if it is updated while the program is running.

Setpwent is identical to setpassent with an argument of zero.

Endpwent closes any open files.

These routines have been written to ``shadow'' the password file, e.g. allow only certain programs to have access to the encrypted password. If the process which calls them has an effective uid of 0, the encrypted password will be returned, otherwise, the password field of the retuned structure will point to the string ``*''.

/var/db/spwd.db The secure password database file

/etc/master.passwd The current password file

/etc/passwd A Version 7 format password file

The routines getpwent , endpwent , setpassent , and setpwent are fairly useless in a networked environment and should be avoided, if possible.