GETPWENT(3)

NAME
getpwent, getpwnam, getpwuid, setpassent, setpwent, endpwent - password database operations

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

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

DESCRIPTION
These functions operate on the password database file which is described in passwd(5). Each entry in the database is defined by the structure passwd found in the include file <pwd.h>:
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;	/* real name */
	char	*pw_dir;	/* home directory */
	char	*pw_shell;	/* default shell */
	time_t	pw_expire;	/* account expiration */
};

The functions getpwnam and getpwuid search the password database for the given login name or user uid, respectively, always returning the first one encountered.

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

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It is dangerous for long-running programs to keep the file descriptors open as the database will become out of date if it is updated while the program is running.

The setpwent function is identical to setpassent with an argument of zero.

The endpwent function 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 returned structure will point to the string *.

YP/NIS INTERACTION
When the yp(4) password database is enabled, the getpwnam and getpwuid functions use the YP maps passwd.byname and passwd.byuid, respectively, if the requested password entry is not found in the local database. The getpwent function will step through the YP map passwd.byname if the entire map is enabled as described in passwd(5).

RETURN VALUES
The functions getpwent, getpwnam, and getpwuid, return a valid pointer to a passwd structure on success and a null pointer if end-of-file is reached or an error occurs. The functions setpassent and setpwent return 0 on failure and 1 on success. The endpwent function has no return value.

FILES

/etc/pwd.db
    The insecure password database file

/etc/spwd.db
    The secure password database file

/etc/master.passwd
    The current password file

/etc/passwd
    A Version 7 format password file

SEE ALSO
getlogin(2), getgrent(3), yp(4), passwd(5), pwd_mkdb(8), vipw(8)

HISTORY
The getpwent, getpwnam, getpwuid, setpwent, and endpwent functions appeared in v7. The setpassent function appeared in 4.3 Reno.

COMPATIBILITY
The historic function setpwfile(3), which allowed the specification of alternate password databases, has been deprecated and is no longer available.

BUGS
The functions getpwent, getpwnam, and getpwuid, leave their results in an internal static object and return a pointer to that object. Subsequent calls to the same function will modify the same object.