GETPWENT(3)

NAME
getpwent, getpwnam, getpwuid, setpwent, endpwent, setpwfile - password file routines

SYNOPSIS
#include <pwd.h>
struct passwd *getpwent(void)
struct passwd *getpwnam(const char *name)
struct passwd *getpwuid(uid_t uid)
int setpwent(void)
void endpwent(void)
void setpwfile(const char *file)

DESCRIPTION
These functions are used to obtain information from the password file. They return this information in a struct passwd as defined by <pwd.h>:

struct passwd {
	char	*pw_name;	/* login name */
	char	*pw_passwd;	/* encrypted password */
	uid_t	pw_uid;	/* numeric user id */
	gid_t	pw_gid;	/* numeric group id */
	char	*pw_gecos;	/* user full name and other info */
	char	*pw_dir;	/* user's home directory */
	char	*pw_shell;	/* name of the user's shell */
};

Getpwent() reads the password file entry by entry. Getpwnam() scans the entire password file for the user with the given name. Getpwuid() looks for the first user with the given uid. The setpwent() and endpwent() functions are used to open and later close the password file. With setpwfile() one can specify the file to read other than the normal password file. This only sets the name, the next setpwent() call will open the file. Do not touch the file name while it is active. Use setpwfile(NULL) to revert back to the normal password file.

The usual way to scan the password file is (error checking omitted):

    setpwent();
    while ((pw = getpwent()) != NULL)
    	if (appropriate_test(pw)) break;
    endpwent();

The pw variable contains the entry that is wanted if non-NULL. The getpwnam() and getpwuid() functions are implemented as in this example, with error checking of course.

Getpwent() calls setpwent() if this has not yet been done. Setpwent() first calls endpwent() if the password file is still open. (Other implementations may simply rewind the file.)

FILES

/etc/passwd
    The password file database.

SEE ALSO
cuserid(3), getlogin(3), getgrent(3), passwd(5).

DIAGNOSTICS
Setpwent() has the same return value and error codes as the open(2) call it uses to open the password file. The getxxx() functions return NULL on end of file, entry not found, or error. You can set errno to zero before the call and check it after.

NOTES
All getxxx() routines return a pointer to static storage that is overwritten in each call.

Only getpwnam() and getpwuid() are defined by POSIX. The _MINIX_SOURCE macro must be defined before including <pwd.h> to make the other functions visible. The pw_passwd and pw_gecos fields are also not defined by POSIX, but are always visible. Portable code cannot reliably detect errors by setting errno to zero. Under Minix it is better to make a getpwent() scan if you need to look up several user-id's or names, but portable code had better use several getpwuid() or getpwnam() calls. The getpwent() is usually available on other systems, but may be very expensive.

AUTHOR
Kees J. Bot (kjb@cs.vu.nl)