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  en‐
33       try  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  de‐
53       scribed  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 at‐
73       tributes(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);
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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

EXAMPLES

106       #define _GNU_SOURCE
107       #include <pwd.h>
108       #include <stdio.h>
109       #include <stdint.h>
110       #define BUFLEN 4096
111
112       int
113       main(void)
114       {
115           struct passwd pw;
116           struct passwd *pwp;
117           char buf[BUFLEN];
118           int i;
119
120           setpwent();
121           while (1) {
122               i = getpwent_r(&pw, buf, sizeof(buf), &pwp);
123               if (i)
124                   break;
125               printf("%s (%jd)\tHOME %s\tSHELL %s\n", pwp->pw_name,
126                      (intmax_t) pwp->pw_uid, pwp->pw_dir, pwp->pw_shell);
127           }
128           endpwent();
129           exit(EXIT_SUCCESS);
130       }
131

COLOPHON

137       This  page  is  part of release 5.10 of the Linux man-pages project.  A
138       description of the project, information about reporting bugs,  and  the
139       latest     version     of     this    page,    can    be    found    at
140       https://www.kernel.org/doc/man-pages/.
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144GNU                               2020-11-01                     GETPWENT_R(3)