NAME
getpwnam, getpwnam_r, getpwuid, getpwuid_r - get password file entry
SYNOPSIS
#include <sys/types.h>
#include <pwd.h>
I struct passwd *getpwnam(const char * name );
I struct passwd *getpwuid(uid_t uid );
I int getpwnam_r(const char * name , struct passwd * pwbuf ,
I char * buf , size_t buflen , struct passwd ** pwbufp );
I int getpwuid_r(uid_t uid , struct passwd * pwbuf ,
I char * buf , size_t buflen , struct passwd ** pwbufp );
DESCRIPTION
The
R 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
R /etc/passwd ,
NIS, and LDAP)
that matches the user name
R name .
The
R 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
R uid .
The
R getpwnam_r ()
and
R getpwuid_r ()
functions obtain the same information, but store the retrieved
passwd
structure in the space pointed to by
R pwbuf .
This
passwd
structure contains pointers to strings, and these strings
are stored in the buffer
buf
of size
R 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
R _SC_GETPW_R_SIZE_MAX
parameter.
RETURN VALUE
The
R getpwnam ()
and
R 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(3),
R getpwnam (),
or
R getpwuid ().
The
R getpwnam_r ()
and
R getpwuid_r ()
functions return
zero on success.
In case of error, an error number is returned.
ERRORS
R 0 or ENOENT or ESRCH or EBADF or EPERM or ...
The given
name
or
uid
was not found.
EINTR
A signal was caught.
EMFILE
The maximum number
(OPEN_MAX)
of files was open already in the calling process.
ENFILE
The maximum number of files was open already in the system.
ENOMEM
Insufficient memory to allocate passwd structure.
ERANGE
Insufficient buffer space supplied.
NOTE
The user password database mostly refers to /etc/passwd.
However, with recent systems it also refers to network wide databases
using NIS, LDAP and other local files as configured in
/etc/nsswitch.conf.
FILES
/etc/passwd
local password database file
/etc/nsswitch.conf
System Databases and Name Service Switch configuration file
CONFORMING TO
SVr4, 4.3BSD, POSIX.1-2001
NOTES
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
R 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.
SEE ALSO
ČLÁNKY DO MAILU