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GETPWENT(3) Library Functions Manual GETPWENT(3)

getpwent, getpwnam, getpwnam_r, getpwuid, getpwuid_r, getpwuuid, getpwuuid_r, setpassent, setpwent, endpwent — password database operations

Standard C Library (libc, -lc)

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

struct passwd *
getpwent(void);

struct passwd *
getpwnam(const char *login);

int
getpwnam_r(const char *name, struct passwd *pwd, char *buffer, size_t bufsize, struct passwd **result);

struct passwd *
getpwuid(uid_t uid);

int
getpwuid_r(uid_t uid, struct passwd *pwd, char *buffer, size_t bufsize, struct passwd **result);

struct passwd *
getpwuuid(uuid_t uuid);

int
getpwuuid_r(uuid_t uuid, struct passwd *pwd, char *buffer, size_t bufsize, struct passwd **result);

int
setpassent(int stayopen);

void
setpwent(void);

void
endpwent(void);

These functions obtain information from opendirectoryd(8), including records in /etc/master.passwd which is described in master.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 */
	int	pw_fields;	/* internal: fields filled in */
};

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

Note that the password file /etc/master.passwd does not contain user UUIDs. The UUID for a user may be found using ().

On OS X, these routines are thread-safe and return a pointer to a thread-specific data structure. The contents of this data structure are automatically released by subsequent calls to any of these routines on the same thread, or when the thread exits. These routines are therefore unsuitable for use in libraries or frameworks, from where they may overwrite the per-thread data that the calling application expects to find as a result of its own calls to these routines. Library and framework code should use the alternative reentrant variants detailed below.

The () function searches all available directory services on its first invocation. It caches the returned entries in a list and returns user account entries one at a time.

that () may cause a very lengthy search for user account records by opendirectoryd and may result in a large number of user account records being cached by the calling process. Use of this function is not advised.

The functions (), (), and () are alternative versions of getpwnam(), getpwuid(), and getpwuuid() respectively. They store the results of their search in the caller-provided pwd structure, which additionally contains pointers to strings that are stored in the caller-provided buffer of size bufsize. (The maximum required bufsize can be obtained by passing the _SC_GETPW_R_SIZE_MAX constant to the sysconf(3) call. See example code below.) When these functions are successful, the pwd argument will be filled in, and a pointer to that argument will be stored in the caller-provided result. If an entry is not found or an error occurs, result will be set to NULL.

The () function causes getpwent() to ``rewind'' to the beginning of the list of entries cached by a previous getpwent() call. The cache is not cleared. The stayopen parameter value is unused on OS X.

The () and () functions clear the cached results from a previous getpwent() call.

These routines have been written to ‘shadow’ the password of user records created on Mac OS X 10.3 or later, by returning a structure whose password field points to the string ‘********’. Legacy crypt passwords are still returned for user records created on earlier versions of Mac OS X whose opendirectoryd(8) attribute contains the value ‘;basic;’.

Note that opendirectoryd(8) allows user records from some sources which may not include all the component fields present in a passwd structure. Only the name, uid, and gid of a user record are required. Default values will be supplied as follows:

pw_passwd = "*"
pw_change = 0
pw_class = ""
pw_gecos = ""
pw_dir = "/var/empty"
pw_shell = "/usr/bin/false"
pw_expire = 0

The functions getpwent(), getpwnam(), getpwuid(), and getpwuuid() return a valid pointer to a passwd structure on success or NULL if the entry is not found or if an error occurs. If an error does occur, errno will be set. Note that programs must explicitly set errno to zero before calling any of these functions if they need to distinguish between a non-existent entry and an error. The functions getpwnam_r(), getpwuid_r(), and getpwuuid_r() return 0 if no error occurred, or an error number to indicate failure. It is not an error if a matching entry is not found. (Thus, if result is NULL and the return value is 0, no matching entry exists.)

The setpassent() function returns 0 on failure and 1 on success. The endpwent() and setpwent() functions have no return value.

To print the current user's home directory without depending on per-thread storage:

#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <pwd.h>

int bufsize;

if ((bufsize = sysconf(_SC_GETPW_R_SIZE_MAX)) == -1)
    abort();

char buffer[bufsize];
struct passwd pwd, *result = NULL;
if (getpwuid_r(getuid(), &pwd, buffer, bufsize, &result) != 0 || !result)
    abort();

printf("%s\n", pwd.pw_dir);

The secure password database file

/etc/master.passwd
The current password file
/etc/passwd
A Version 7 format password file

These routines may fail for any of the errors specified in open(2), dbopen(3), socket(2), and connect(2), in addition to the following:

[]
The buffer specified by the buffer and bufsize arguments was insufficiently sized to store the result. The caller should retry with a larger buffer.

getlogin(2), getgrent(3), passwd(5), mbr_uid_to_uuid(3,) opendirectoryd(8), yp(8)

The getpwent(), getpwnam(), getpwnam_r(), getpwuid(), getpwuid_r(), setpwent(), and endpwent() functions conform to ISO/IEC 9945-1:1996 (“POSIX.1”).

The getpwent(), getpwnam(), getpwuid(), setpwent(), and endpwent() functions appeared in Version 7 AT&T UNIX. The setpassent() function appeared in 4.3BSD-Reno. The getpwnam_r() and getpwuid_r() functions appeared in FreeBSD 5.1. The functions getpwuuid() and getpwuuid_r() appeared in Mac OS X 10.8.

The functions getpwent(), getpwnam(), getpwuid(), and getpwuuid(), leave their results in an internal thread-specific memory and return a pointer to that object. Subsequent calls to the same function will modify the same object.

October 26, 2011 macOS