GETPWENT(3)

GETPWENT(3) | Library Functions Manual | GETPWENT(3)

# NAME

`getpwent`, `getpwent_r`, `getpwnam`, `getpwnam_r`, `getpwuid`, `getpwuid_r`, `setpassent`, `setpwent`, `endpwent` —
password database operations

# LIBRARY

Standard C Library (libc, -lc)

# SYNOPSIS

`#include <pwd.h>`

struct passwd *
`getpwent`(void);

int
`getpwent_r`(struct passwd *pw, char *buffer, size_t buflen, struct passwd **result);

struct passwd *
`getpwnam`(const char *name);

int
`getpwnam_r`(const char *name, struct passwd *pw, char *buffer, size_t buflen, struct passwd **result);

struct passwd *
`getpwuid`(uid_t uid);

int
`getpwuid_r`(uid_t uid, struct passwd *pw, char *buffer, size_t buflen, struct passwd **result);

int
`setpassent`(int stayopen);

void
`setpwent`(void);

void
`endpwent`(void);

# DESCRIPTION

These functions operate on the password database 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 login class */
    	char	*pw_gecos;	/* general information */
    	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 user name pointed to by name or user id pointed to by uid respectively, always returning the first one encountered. Identical user names or user ids may result in undefined behavior.

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

The functions `getpwnam_r`(), `getpwuid_r`(), and `getpwent_r`() act like their non re-entrant counterparts, updating the contents of pw and storing a pointer to that in result, and returning `0`. Storage used by pw is allocated from buffer, which is buflen bytes in size. If the requested entry cannot be found, result will point to `NULL` and `0` will be returned. If an error occurs, a non-zero error number will be returned and result will point to `NULL`. Calling `getpwent_r`() from multiple threads will result in each thread reading a disjoint portion of the password database.

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 functions. (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 equivalent to `setpassent`() with an argument of zero.

The `endpwent`() function closes any open files.

These functions 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 ‘`*`’.

# RETURN VALUES

The functions `getpwent`(), `getpwnam`(), and `getpwuid`(), return a valid pointer to a passwd structure on success and a `NULL` pointer if the entry was not found or an error occurred. If an error occurred, the global variable `errno` is set to indicate the nature of the failure. The `setpassent`() function returns 0 on failure, setting the global variable `errno` to indicate the nature of the failure, and 1 on success. The `endpwent`() and `setpwent`() functions have no return value. The functions `getpwnam_r`(), `getpwuid_r`(), and `getpwent_r`() return `0` on success or entry not found, and non-zero on failure, setting the global variable `errno` to indicate the nature of the failure.

# 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

# COMPATIBILITY

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

# ERRORS

The following error codes may be set in errno for `getpwent`, `getpwent_r`, `getpwnam`, `getpwnam_r`, `getpwuid`, `getpwuid_r`, and `setpassent`:

[`EINTR`]
  A signal was caught during the database search.
[`EIO`]
  An I/O error has occurred.
[`EMFILE`]
  The limit on open files for this process has been reached.
[`ENFILE`]
  The system limit on open files has been reached.

The following error code may be set in errno for `getpwent_r`, `getpwnam_r`, and `getpwuid_r`:

[`ERANGE`]
  The resulting struct passwd does not fit in the space defined by `buffer` and `buflen`.

Other `errno` values may be set depending on the specific database backends.

# SEE ALSO

getlogin(2), getgrent(3), nsswitch.conf(5), passwd(5), passwd.conf(5), pwd_mkdb(8), vipw(8)

# STANDARDS

The `getpwnam`() and `getpwuid`(), functions conform to IEEE Std 1003.1-1990 (“POSIX.1”). The `getpwnam_r`() and `getpwuid_r`() functions conform to IEEE Std 1003.1c-1995 (“POSIX.1c”). The `endpwent`(), `getpwent`(), and `setpwent`() functions conform to X/Open Portability Guide Issue 4, Version 2 (“XPG4.2”) and IEEE Std 1003.1-2004 (“POSIX.1”) (XSI extension).

# HISTORY

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 `getpwnam_r`() and `getpwuid_r`() appeared in NetBSD 3.0.

# 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 any of these functions will modify the same object.

The functions `getpwent`(), `endpwent`(), `setpassent`(), and `setpwent`() are fairly useless in a networked environment and should be avoided, if possible. `getpwent`() makes no attempt to suppress duplicate information if multiple sources are specified in nsswitch.conf(5).

February 7, 2018 | NetBSD 9.3