1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
3 .\" <mtk.manpages@gmail.com>
5 .\" %%%LICENSE_START(VERBATIM)
6 .\" Permission is granted to make and distribute verbatim copies of this
7 .\" manual provided the copyright notice and this permission notice are
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10 .\" Permission is granted to copy and distribute modified versions of this
11 .\" manual under the conditions for verbatim copying, provided that the
12 .\" entire resulting derived work is distributed under the terms of a
13 .\" permission notice identical to this one.
15 .\" Since the Linux kernel and libraries are constantly changing, this
16 .\" manual page may be incorrect or out-of-date. The author(s) assume no
17 .\" responsibility for errors or omissions, or for damages resulting from
18 .\" the use of the information contained herein. The author(s) may not
19 .\" have taken the same level of care in the production of this manual,
20 .\" which is licensed free of charge, as they might when working
23 .\" Formatted or processed versions of this manual, if unaccompanied by
24 .\" the source, must acknowledge the copyright and authors of this work.
27 .\" References consulted:
28 .\" Linux libc source code
29 .\" Lewine's "POSIX Programmer's Guide" (O'Reilly & Associates, 1991)
32 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
33 .\" Modified 1996-05-27 by Martin Schulze (joey@linux.de)
34 .\" Modified 2003-11-15 by aeb
35 .\" 2008-11-07, mtk, Added an example program for getpwnam_r().
37 .TH GETPWNAM 3 2021-03-22 "GNU" "Linux Programmer's Manual"
39 getpwnam, getpwnam_r, getpwuid, getpwuid_r \- get password file entry
42 .B #include <sys/types.h>
45 .BI "struct passwd *getpwnam(const char *" name );
46 .BI "struct passwd *getpwuid(uid_t " uid );
48 .BI "int getpwnam_r(const char *restrict " name \
49 ", struct passwd *restrict " pwd ,
50 .BI " char *restrict " buf ", size_t " buflen ,
51 .BI " struct passwd **restrict " result );
52 .BI "int getpwuid_r(uid_t " uid ", struct passwd *restrict " pwd ,
53 .BI " char *restrict " buf ", size_t " buflen ,
54 .BI " struct passwd **restrict " result );
58 Feature Test Macro Requirements for glibc (see
59 .BR feature_test_macros (7)):
66 || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
71 function returns a pointer to a structure containing
72 the broken-out fields of the record in the password database
73 (e.g., the local password file
76 that matches the username
81 function returns a pointer to a structure containing
82 the broken-out fields of the record in the password database
83 that matches the user ID
86 The \fIpasswd\fP structure is defined in \fI<pwd.h>\fP as follows:
91 char *pw_name; /* username */
92 char *pw_passwd; /* user password */
93 uid_t pw_uid; /* user ID */
94 gid_t pw_gid; /* group ID */
95 char *pw_gecos; /* user information */
96 char *pw_dir; /* home directory */
97 char *pw_shell; /* shell program */
104 for more information about these fields.
110 functions obtain the same information as
114 but store the retrieved
116 structure in the space pointed to by
118 The string fields pointed to by the members of the
120 structure are stored in the buffer
124 A pointer to the result (in case of success) or NULL (in case no entry
125 was found or an error occurred) is stored in
130 sysconf(_SC_GETPW_R_SIZE_MAX)
132 returns either \-1, without changing
134 or an initial suggested size for
136 (If this size is too small,
139 in which case the caller can retry with a larger buffer.)
145 functions return a pointer to a
147 structure, or NULL if the matching entry is not found or
151 is set to indicate the error.
152 If one wants to check
154 after the call, it should be set to zero before the call.
156 The return value may point to a static area, and may be overwritten
157 by subsequent calls to
162 (Do not pass the returned pointer to
173 If no matching password record was found,
174 these functions return 0 and store NULL in
176 In case of error, an error number is returned, and NULL is stored in
180 .BR 0 " or " ENOENT " or " ESRCH " or " EBADF " or " EPERM " or ..."
188 A signal was caught; see
195 The per-process limit on the number of open file descriptors has been reached.
198 The system-wide limit on the total number of open files has been reached.
202 Insufficient memory to allocate
205 .\" This structure is static, allocated 0 or 1 times. No memory leak. (libc45)
208 Insufficient buffer space supplied.
212 local password database file
214 For an explanation of the terms used in this section, see
222 Interface Attribute Value
226 MT-Unsafe race:pwnam locale
231 MT-Unsafe race:pwuid locale
244 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
247 field is not specified in POSIX, but is present on most implementations.
249 The formulation given above under "RETURN VALUE" is from POSIX.1-2001.
250 It does not call "not found" an error, and hence does not specify what value
252 might have in this situation.
253 But that makes it impossible to recognize
255 One might argue that according to POSIX
257 should be left unchanged if an entry is not found.
258 Experiments on various
259 UNIX-like systems show that lots of different values occur in this
260 situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably others.
262 .\" AIX 5.1 - gives ESRCH
263 .\" OSF1 4.0g - gives EWOULDBLOCK
264 .\" libc, glibc up to version 2.6, Irix 6.5 - give ENOENT
265 .\" glibc since version 2.7 - give 0
266 .\" FreeBSD 4.8, OpenBSD 3.2, NetBSD 1.6 - give EPERM
267 .\" SunOS 5.8 - gives EBADF
268 .\" Tru64 5.1b, HP-UX-11i, SunOS 5.7 - give 0
272 field contains the name of the initial working directory of the user.
273 Login programs use the value of this field to initialize the
275 environment variable for the login shell.
276 An application that wants to determine its user's home directory
277 should inspect the value of
279 (rather than the value
280 .IR getpwuid(getuid())\->pw_dir )
281 since this allows the user to modify their notion of
282 "the home directory" during a login session.
283 To determine the (initial) home directory of another user,
284 it is necessary to use
285 .I getpwnam("username")\->pw_dir
288 The program below demonstrates the use of
290 to find the full username and user ID for the username
291 supplied as a command-line argument.
302 main(int argc, char *argv[])
305 struct passwd *result;
311 fprintf(stderr, "Usage: %s username\en", argv[0]);
315 bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
316 if (bufsize == \-1) /* Value was indeterminate */
317 bufsize = 16384; /* Should be more than enough */
319 buf = malloc(bufsize);
325 s = getpwnam_r(argv[1], &pwd, buf, bufsize, &result);
326 if (result == NULL) {
328 printf("Not found\en");
331 perror("getpwnam_r");
336 printf("Name: %s; UID: %jd\en", pwd.pw_gecos,
337 (intmax_t) pwd.pw_uid);