1GETPWNAM(3) Linux Programmer's Manual GETPWNAM(3)
2
6 getpwnam, getpwnam_r, getpwuid, getpwuid_r - get password file entry
7
9 #include <sys/types.h>
10 #include <pwd.h>
11 struct passwd *getpwnam(const char *name);
13 struct passwd *getpwuid(uid_t uid);
15 int getpwnam_r(const char *name, struct passwd *pwd,
17 char *buf, size_t buflen, struct passwd **result);
18 int getpwuid_r(uid_t uid, struct passwd *pwd,
20 char *buf, size_t buflen, struct passwd **result);
21 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
23 getpwnam_r(), getpwuid_r():
25 _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _BSD_SOURCE ||
26 _SVID_SOURCE || _POSIX_SOURCE
27
29 The getpwnam() function returns a pointer to a structure containing the
30 broken-out fields of the record in the password database (e.g., the
31 local password file /etc/passwd, NIS, and LDAP) that matches the user‐
32 name name.
33 The getpwuid() function returns a pointer to a structure containing the
35 broken-out fields of the record in the password database that matches
36 the user ID uid.
37 The passwd structure is defined in <pwd.h> as follows:
39 struct passwd {
41 char *pw_name; /* username */
42 char *pw_passwd; /* user password */
43 uid_t pw_uid; /* user ID */
44 gid_t pw_gid; /* group ID */
45 char *pw_gecos; /* user information */
46 char *pw_dir; /* home directory */
47 char *pw_shell; /* shell program */
48 };
49 See passwd(5) for more information about these fields.
51 The getpwnam_r() and getpwuid_r() functions obtain the same information
53 as getpwnam() and getpwuid(), but store the retrieved passwd structure
54 in the space pointed to by pwd. The string fields pointed to by the
55 members of the passwd structure are stored in the buffer buf of size
56 buflen. A pointer to the result (in case of success) or NULL (in case
57 no entry was found or an error occurred) is stored in *result.
58 The call
60 sysconf(_SC_GETPW_R_SIZE_MAX)
62 returns either -1, without changing errno, or an initial suggested size
64 for buf. (If this size is too small, the call fails with ERANGE, in
65 which case the caller can retry with a larger buffer.)
66
68 The getpwnam() and getpwuid() functions return a pointer to a passwd
69 structure, or NULL if the matching entry is not found or an error
70 occurs. If an error occurs, errno is set appropriately. If one wants
71 to check errno after the call, it should be set to zero before the
72 call.
73 The return value may point to a static area, and may be overwritten by
75 subsequent calls to getpwent(3), getpwnam(), or getpwuid(). (Do not
76 pass the returned pointer to free(3).)
77 On success, getpwnam_r() and getpwuid_r() return zero, and set *result
79 to pwd. If no matching password record was found, these functions
80 return 0 and store NULL in *result. In case of error, an error number
81 is returned, and NULL is stored in *result.
82
84 0 or ENOENT or ESRCH or EBADF or EPERM or ...
85 The given name or uid was not found.
86 EINTR A signal was caught.
88 EIO I/O error.
90 EMFILE The maximum number (OPEN_MAX) of files was open already in the
92 calling process.
93 ENFILE The maximum number of files was open already in the system.
95 ENOMEM Insufficient memory to allocate passwd structure.
97 ERANGE Insufficient buffer space supplied.
99
101 /etc/passwd
102 local password database file
103
105 Multithreading (see pthreads(7))
106 The getpwnam() and getpwuid() functions are not thread-safe.
107 The getpwnam_r() and getpwuid_r() functions are thread-safe.
109
111 SVr4, 4.3BSD, POSIX.1-2001. The pw_gecos field is not specified in
112 POSIX, but is present on most implementations.
113
115 The formulation given above under "RETURN VALUE" is from POSIX.1-2001.
116 It does not call "not found" an error, and hence does not specify what
117 value errno might have in this situation. But that makes it impossible
118 to recognize errors. One might argue that according to POSIX errno
119 should be left unchanged if an entry is not found. Experiments on var‐
120 ious UNIX-like systems show that lots of different values occur in this
121 situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and probably
122 others.
123 The pw_dir field contains the name of the initial working directory of
125 the user. Login programs use the value of this field to initialize the
126 HOME environment variable for the login shell. An application that
127 wants to determine its user's home directory should inspect the value
128 of HOME (rather than the value getpwuid(getuid())->pw_dir) since this
129 allows the user to modify their notion of "the home directory" during a
130 login session. To determine the (initial) home directory of another
131 user, it is necessary to use getpwnam("username")->pw_dir or similar.
132
134 The program below demonstrates the use of getpwnam_r() to find the full
135 username and user ID for the username supplied as a command-line argu‐
136 ment.
137 #include <pwd.h>
139 #include <stdio.h>
140 #include <stdlib.h>
141 #include <unistd.h>
142 #include <errno.h>
143 int
145 main(int argc, char *argv[])
146 {
147 struct passwd pwd;
148 struct passwd *result;
149 char *buf;
150 size_t bufsize;
151 int s;
152 if (argc != 2) {
154 fprintf(stderr, "Usage: %s username\n", argv[0]);
155 exit(EXIT_FAILURE);
156 }
157 bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
159 if (bufsize == -1) /* Value was indeterminate */
160 bufsize = 16384; /* Should be more than enough */
161 buf = malloc(bufsize);
163 if (buf == NULL) {
164 perror("malloc");
165 exit(EXIT_FAILURE);
166 }
167 s = getpwnam_r(argv[1], &pwd, buf, bufsize, &result);
169 if (result == NULL) {
170 if (s == 0)
171 printf("Not found\n");
172 else {
173 errno = s;
174 perror("getpwnam_r");
175 }
176 exit(EXIT_FAILURE);
177 }
178 printf("Name: %s; UID: %ld\n", pwd.pw_gecos, (long) pwd.pw_uid);
180 exit(EXIT_SUCCESS);
181 }
182
184 endpwent(3), fgetpwent(3), getgrnam(3), getpw(3), getpwent(3), getsp‐
185 nam(3), putpwent(3), setpwent(3), passwd(5)
186
188 This page is part of release 3.53 of the Linux man-pages project. A
189 description of the project, and information about reporting bugs, can
190 be found at http://www.kernel.org/doc/man-pages/.
191GNU 2013-07-22 GETPWNAM(3)