getpwnam, getpwnam_r, getpwuid, getpwuid_r — get password file entry
#include <sys/types.h> #include <pwd.h>
struct passwd *getpwnam( |
const char * | name) ; |
struct passwd *getpwuid( |
uid_t | uid) ; |
int
getpwnam_r( |
const char * | name, |
struct passwd * | pwbuf, | |
char * | buf, | |
size_t | buflen, | |
struct passwd ** | pwbufp) ; |
int
getpwuid_r( |
uid_t | uid, |
struct passwd * | pwbuf, | |
char * | buf, | |
size_t | buflen, | |
struct passwd ** | pwbufp) ; |
The getpwnam
() function
returns a pointer to a structure containing the broken-out
fields of the record in the password database (e.g., the
local password file /etc/passwd
, NIS, and LDAP) that matches
the user name name
.
The getpwuid
() function
returns a pointer to a structure containing the broken-out
fields of the record in the password database that matches
the user ID uid
.
The getpwnam_r
() and
getpwuid_r
() functions obtain
the same information, but store the retrieved passwd
structure in the space
pointed to by pwbuf
.
This passwd
structure contains pointers to strings, and these strings are
stored in the buffer buf
of size buflen
. A pointer to the result
(in case of success) or NULL (in case no entry was found or
an error occurred) is stored in *pwbufp
.
The passwd
structure is defined in <pwd.h>
as follows:
struct passwd { }; char * pw_name
;/* user name */ char * pw_passwd
;/* user password */ uid_t pw_uid
;/* user ID */ gid_t pw_gid
;/* group ID */ char * pw_gecos
;/* real name */ char * pw_dir
;/* home directory */ char * pw_shell
;/* shell program */
The maximum needed size for buf
can be found using sysconf(3) with the
_SC_GETPW_R_SIZE_MAX parameter.
The getpwnam
() and
getpwuid
() functions return a
pointer to a passwd
structure, or NULL if the matching entry is not found or an
error occurs. If an error occurs, errno
is set appropriately. If one wants to
check errno
after the call, it
should be set to zero before the call.
The return value may point to static area, and may be
overwritten by subsequent calls to getpwent
(), getpwnam
(), or getpwuid
().
The getpwnam_r
() and
getpwuid_r
() functions return
zero on success. In case of error, an error number is
returned.
0
or
ENOENT or ESRCH or EBADF or EPERM or ...The given name
or uid
was not found.
A signal was caught.
I/O error.
The maximum number (OPEN_MAX) of files was open already in the calling process.
The maximum number of files was open already in the system.
Insufficient memory to allocate passwd structure.
Insufficient buffer space supplied.
The formulation given above under "RETURN VALUE" is from
POSIX.1-2001. It does not call "not found" an error, and
hence does not specify what value errno
might have in this situation. But that
makes it impossible to recognize errors. One might argue that
according to POSIX errno
should
be left unchanged if an entry is not found. Experiments on
various Unix-like systems show that lots of different values
occur in this situation: 0, ENOENT, EBADF, ESRCH,
EWOULDBLOCK, EPERM and probably others.
The pw_dir
field
contains the name of the initial working directory of the
user. Login programs use the value of this field to
initialize the HOME environment variable for the login shell.
An application that wants to determine its user's home
directory should inspect the value of HOME (rather than the
value getpwuid(getuid())->pw_dir
)
since this allows the user to modify their notion of "the
home directory" during a login session. To determine the
(initial) home directory of another user, it is necessary to
use getpwnam("username")->pw_dir
or similar.
endpwent(3), fgetpwent(3), getgrnam(3), getpw(3), getpwent(3), putpwent(3), setpwent(3), passwd(5)
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