getpwent_r(3)

1GETPWENT_R(3)              Linux Programmer's Manual             GETPWENT_R(3)
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NAME

6       getpwent_r, fgetpwent_r - get passwd file entry reentrantly
7

SYNOPSIS

9       #include <pwd.h>
10
11       int getpwent_r(struct passwd *pwbuf, char *buf,
12                      size_t buflen, struct passwd **pwbufp);
13
14       int fgetpwent_r(FILE *stream, struct passwd *pwbuf, char *buf,
15                       size_t buflen, struct passwd **pwbufp);
16
17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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19       getpwent_r(),
20           Since glibc 2.19:
21               _DEFAULT_SOURCE
22           Glibc 2.19 and earlier:
23               _BSD_SOURCE || _SVID_SOURCE
24       fgetpwent_r():
25           Since glibc 2.19:
26               _DEFAULT_SOURCE
27           Glibc 2.19 and earlier:
28               _SVID_SOURCE
29

DESCRIPTION

31       The functions getpwent_r() and fgetpwent_r() are the reentrant versions
32       of getpwent(3) and fgetpwent(3).  The  former  reads  the  next  passwd
33       entry from the stream initialized by setpwent(3).  The latter reads the
34       next passwd entry from stream.
35
36       The passwd structure is defined in <pwd.h> as follows:
37
38           struct passwd {
39               char    *pw_name;      /* username */
40               char    *pw_passwd;    /* user password */
41               uid_t    pw_uid;       /* user ID */
42               gid_t    pw_gid;       /* group ID */
43               char    *pw_gecos;     /* user information */
44               char    *pw_dir;       /* home directory */
45               char    *pw_shell;     /* shell program */
46           };
47
48       For more information about the fields of this structure, see passwd(5).
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50       The nonreentrant functions return a pointer to  static  storage,  where
51       this  static  storage contains further pointers to user name, password,
52       gecos  field,  home  directory  and  shell.   The  reentrant  functions
53       described here return all of that in caller-provided buffers.  First of
54       all there is the buffer pwbuf that can hold a struct passwd.  And  next
55       the  buffer  buf  of size buflen that can hold additional strings.  The
56       result of these functions, the struct passwd read from the  stream,  is
57       stored  in  the  provided  buffer  *pwbuf, and a pointer to this struct
58       passwd is returned in *pwbufp.
59

RETURN VALUE

61       On success, these functions return 0 and *pwbufp is a  pointer  to  the
62       struct  passwd.   On  error,  these functions return an error value and
63       *pwbufp is NULL.
64

ERRORS

66       ENOENT No more entries.
67
68       ERANGE Insufficient buffer space supplied.  Try again with larger  buf‐
69              fer.
70

ATTRIBUTES

72       For   an   explanation   of   the  terms  used  in  this  section,  see
73       attributes(7).
74
75       ┌──────────────┬───────────────┬─────────────────────────────┐
76       │Interface     │ Attribute     │ Value                       │
77       ├──────────────┼───────────────┼─────────────────────────────┤
78       │getpwent_r()  │ Thread safety │ MT-Unsafe race:pwent locale │
79       ├──────────────┼───────────────┼─────────────────────────────┤
80       │fgetpwent_r() │ Thread safety │ MT-Safe                     │
81       └──────────────┴───────────────┴─────────────────────────────┘
82       In the above table, pwent in race:pwent signifies that if  any  of  the
83       functions  setpwent(), getpwent(), endpwent(), or getpwent_r() are used
84       in parallel in different threads of a program, then  data  races  could
85       occur.
86

CONFORMING TO

88       These  functions  are  GNU  extensions,  done in a style resembling the
89       POSIX version of functions like getpwnam_r(3).  Other systems  use  the
90       prototype
91
92           struct passwd *
93           getpwent_r(struct passwd *pwd, char *buf, int buflen);
94
95       or, better,
96
97           int
98           getpwent_r(struct passwd *pwd, char *buf, int buflen,
99                      FILE **pw_fp);
100

NOTES

102       The  function  getpwent_r() is not really reentrant since it shares the
103       reading position in the stream with all other threads.
104

EXAMPLE

106       #define _GNU_SOURCE
107       #include <pwd.h>
108       #include <stdio.h>
109       #define BUFLEN 4096
110
111       int
112       main(void)
113       {
114           struct passwd pw, *pwp;
115           char buf[BUFLEN];
116           int i;
117
118           setpwent();
119           while (1) {
120               i = getpwent_r(&pw, buf, BUFLEN, &pwp);
121               if (i)
122                   break;
123               printf("%s (%d)\tHOME %s\tSHELL %s\n", pwp->pw_name,
124                      pwp->pw_uid, pwp->pw_dir, pwp->pw_shell);
125           }
126           endpwent();
127           exit(EXIT_SUCCESS);
128       }
129

COLOPHON

135       This  page  is  part of release 4.15 of the Linux man-pages project.  A
136       description of the project, information about reporting bugs,  and  the
137       latest     version     of     this    page,    can    be    found    at
138       https://www.kernel.org/doc/man-pages/.
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142GNU                               2017-09-15                     GETPWENT_R(3)