NAME
getpwnam
,
getpwuid
, getpwnam_r
,
getpwuid_r
, setpassent
— password database
operations
SYNOPSIS
#include
<sys/types.h>
#include <pwd.h>
struct passwd *
getpwnam
(const
char *login);
struct passwd *
getpwuid
(uid_t
uid);
int
getpwnam_r
(const
char *login, struct
passwd *pwstore, char
*buf, size_t
buflen, struct passwd
**result);
int
getpwuid_r
(uid_t
uid, struct passwd
*pwstore, char
*buf, size_t
buflen, struct passwd
**result);
int
setpassent
(int
stayopen);
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 struct 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
getpwnam
()
and
getpwuid
()
search the password database for the given login name or user ID,
respectively, always returning the first one encountered.
The re-entrant versions,
getpwnam_r
()
and
getpwuid_r
(),
behave similarly but the various strings associated with the result are
stored in buf, and pwstore is
updated to reference those strings.
setpassent
()
accomplishes two purposes. First, it causes
getpwent(3) 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
the lookup routines. These file descriptors can be closed by a call to
endpwent(3).
It is dangerous for long-running programs to keep the file descriptors open as the database will become out of date if it is updated while the program is running. Furthermore, programs that run child processes should be careful to call endpwent(3) to close these descriptors before calling execve(2) or system(3).
These routines have been written to “shadow” the
password file, that is, allow only certain programs to have access to the
encrypted password. If the process which calls them has an effective UID of
0 or has the “_shadow” group in its group vector, the
encrypted password will be returned, otherwise, the password field of the
returned structure will point to the string
‘*
’.
YP SUPPORT
If YP is active, the functions
getpwnam
()
and getpwnam_r
() also use the
master.passwd.byname YP map (if available) or the
passwd.byname YP map; and the functions
getpwuid
() and getpwuid_r
()
also use the master.passwd.byuid YP map (if
available) or the passwd.byuid YP map. This is in
addition to the passwd file, and respects the order of both normal and YP
entries in the passwd file.
RETURN VALUES
The functions getpwnam
() and
getpwuid
() return a valid pointer to a passwd
structure on success or a null pointer if end-of-file is reached or an error
occurs.
The functions getpwnam_r
() and
getpwuid_r
() update result to
point to pwstore and then return 0 on success.
The setpassent
() function returns 0 on
failure or 1 on success.
FILES
- /etc/pwd.db
- insecure password database file
- /etc/spwd.db
- secure password database file
- /etc/master.passwd
- current password file
- /etc/passwd
- a Version 7 format password file
SEE ALSO
getlogin(2), getgrent(3), getgrouplist(3), getpwent(3), pw_dup(3), passwd(5), Makefile.yp(8), pwd_mkdb(8), vipw(8), yp(8)
HISTORY
The getpwnam
() and
getpwuid
() functions appeared in
Version 7 AT&T UNIX. The
setpassent
() function appeared in
4.3BSD-Reno.
BUGS
The getpwnam
() and
getpwuid
() functions store their results in an
internal static buffer and return a pointer to that buffer. Subsequent calls
to getpwent
(), getpwnam
(),
or getpwuid
() will overwrite the same buffer.