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[thirdparty/man-pages.git] / man3 / getpwnam.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's "POSIX Programmer's Guide" (O'Reilly & Associates, 1991)
.\"     386BSD man pages
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.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 1996-05-27 by Martin Schulze (joey@linux.de)
.\" Modified 2003-11-15 by aeb
.\"
.TH GETPWNAM 3  1996-05-27 "GNU" "Linux Programmer's Manual"
.SH NAME
getpwnam, getpwnam_r, getpwuid, getpwuid_r \- get password file entry
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.B #include <pwd.h>
.sp
.BI "struct passwd *getpwnam(const char *" name );
.sp
.BI "struct passwd *getpwuid(uid_t " uid );
.sp
.BI "int getpwnam_r(const char *" name ", struct passwd *" pwbuf ,
.br
.BI "        char *" buf ", size_t " buflen ", struct passwd **" pwbufp );
.sp
.BI "int getpwuid_r(uid_t " uid ", struct passwd *" pwbuf ,
.br
.BI "        char *" buf ", size_t " buflen ", struct passwd **" pwbufp );
.fi
.SH DESCRIPTION
The
.BR 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
.IR /etc/passwd ,
NIS, and LDAP)
that matches the user name
.IR name .
.PP
The
.BR 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
.IR uid .
.PP
The
.BR getpwnam_r ()
and
.BR getpwuid_r ()
functions obtain the same information, but store the retrieved
.I passwd
structure in the space pointed to by
.IR pwbuf .
This
.I passwd
structure contains pointers to strings, and these strings
are stored in the buffer
.I buf
of size
.IR 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
.RI * pwbufp .
.PP
The \fIpasswd\fP structure is defined in \fI<pwd.h>\fP as follows:
.sp
.RS 0.25i
.nf
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 */
};
.fi
.RE
.PP
The maximum needed size for
.I buf
can be found using
.BR sysconf (3)
with the _SC_GETPW_R_SIZE_MAX parameter.
.SH "RETURN VALUE"
The \fBgetpwnam\fP() and \fBgetpwuid\fP() functions return a pointer to a
.I passwd
structure, or NULL if the matching entry is not found or
an error occurs.
If an error occurs,
.I errno
is set appropriately.
If one wants to check
.I errno
after the call, it should be set to zero before the call.
.LP
The return value may point to static area, and may be overwritten
by subsequent calls to
.BR getpwent (),
.BR getpwnam (),
or
.BR getpwuid ().
.LP
The  \fBgetpwnam_r\fP() and \fBgetpwuid_r\fP() functions return
zero on success.
In case of error, an error number is returned.
.SH ERRORS
.TP
.BR 0 " or " ENOENT " or " ESRCH " or " EBADF " or " EPERM " or ... "
The given
.I name
or
.I uid
was not found.
.TP
.B EINTR
A signal was caught.
.TP
.B EIO
I/O error.
.TP
.B EMFILE
The maximum number (OPEN_MAX) of files was open already in the calling process.
.TP
.B ENFILE
The maximum number of files was open already in the system.
.TP
.B ENOMEM
.\" not in POSIX
Insufficient memory to allocate passwd structure.
.\" This structure is static, allocated 0 or 1 times. No memory leak. (libc45)
.TP
.B ERANGE
Insufficient buffer space supplied.
.SH FILES
.TP
.I /etc/passwd
local password database file
.fi
.SH "CONFORMING TO"
SVr4, 4.3BSD, POSIX.1-2001
.SH 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
.I errno
might have in this situation.
But that makes it impossible to recognize
errors.
One might argue that according to POSIX
.I 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.
.\" more precisely:
.\" AIX 5.1 - gives ESRCH
.\" OSF1 4.0g - gives EWOULDBLOCK
.\" libc, glibc, Irix 6.5 - give ENOENT
.\" FreeBSD 4.8, OpenBSD 3.2, NetBSD 1.6 - give EPERM
.\" SunOS 5.8 - gives EBADF
.\" Tru64 5.1b, HP-UX-11i, SunOS 5.7 - give 0

The
.I 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
.IR 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
.I getpwnam("username")->pw_dir
or similar.
.SH "SEE ALSO"
.BR endpwent (3),
.BR fgetpwent (3),
.BR getgrnam (3),
.BR getpw (3),
.BR getpwent (3),
.BR putpwent (3),
.BR setpwent (3),
.BR passwd (5)