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GETPWENT(3) Library Functions Manual GETPWENT(3)

getpwent, getpwnam, getpwuid, setpassent, setpwent, endpwent — password database operations

#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);

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;	/* Honeywell login info */
	char	*pw_dir;	/* home directory */
	char	*pw_shell;	/* default shell */
	time_t	pw_expire;	/* account expiration */
};

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

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

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It is dangerous for long-running programs to keep the file descriptors open as the database will become out of date if it is updated while the program is running.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

The () 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 ‘*’.

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.

/var/db/pwd.db
The insecure password database file
/var/db/spwd.db
The secure password database file
/etc/master.passwd
The current password file
/etc/passwd
A Version 7 format password file

getlogin(3), getgrent(3), passwd(5), pwd_mkdb(8), vipw(8)

The getpwent, getpwnam, getpwuid, setpwent, and endpwent functions appeared in Version 7 AT&T UNIX. The setpassent function appeared in 4.3BSD-Reno.

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.

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

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

4.4BSD-Lite2 December 11, 1993 GETPWENT(3)