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NAME
getpwnam, getpwnam_r, getpwuid, getpwuid_r - get password file entry
SYNOPSIS
#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);
DESCRIPTION
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 informa‐
tion, 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(3), getpwnam(), or getpwuid().
The getpwnam_r() and getpwuid_r() functions return zero on success. In
case of error, an error number is returned.
ERRORS
0 or ENOENT or ESRCH or EBADF or EPERM or ...
The given name or uid was not found.
EINTR A signal was caught.
EIO I/O error.
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
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 var‐
ious 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), putp
went(3), setpwent(3), nsswitch.conf(5), passwd(5)