getpwent_r(3)

1GETPWENT_R(3)              Linux Programmer's Manual             GETPWENT_R(3)
2
3
4

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 *fp, 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)):
18
19       getpwent_r(), _BSD_SOURCE || _SVID_SOURCE
20       fgetpwent_r(): _SVID_SOURCE
21

DESCRIPTION

23       The functions getpwent_r() and fgetpwent_r() are the reentrant versions
24       of getpwent(3) and fgetpwent(3).  The  former  reads  the  next  passwd
25       entry from the stream initialized by setpwent(3).  The latter reads the
26       next passwd entry from the stream fp.
27
28       The passwd structure is defined in <pwd.h> as follows:
29
30           struct passwd {
31               char    *pw_name;      /* username */
32               char    *pw_passwd;    /* user password */
33               uid_t    pw_uid;       /* user ID */
34               gid_t    pw_gid;       /* group ID */
35               char    *pw_gecos;     /* user information */
36               char    *pw_dir;       /* home directory */
37               char    *pw_shell;     /* shell program */
38           };
39
40       For more information about the fields of this structure, see passwd(5).
41
42       The nonreentrant functions return a pointer to  static  storage,  where
43       this  static  storage contains further pointers to user name, password,
44       gecos  field,  home  directory  and  shell.   The  reentrant  functions
45       described here return all of that in caller-provided buffers.  First of
46       all there is the buffer pwbuf that can hold a struct passwd.  And  next
47       the  buffer  buf  of size buflen that can hold additional strings.  The
48       result of these functions, the struct passwd read from the  stream,  is
49       stored  in  the  provided  buffer  *pwbuf, and a pointer to this struct
50       passwd is returned in *pwbufp.
51

RETURN VALUE

53       On success, these functions return 0 and *pwbufp is a  pointer  to  the
54       struct  passwd.   On  error,  these functions return an error value and
55       *pwbufp is NULL.
56

ERRORS

58       ENOENT No more entries.
59
60       ERANGE Insufficient buffer space supplied.  Try again with larger  buf‐
61              fer.
62

CONFORMING TO

64       These  functions  are  GNU  extensions,  done in a style resembling the
65       POSIX version of functions like getpwnam_r(3).  Other systems use  pro‐
66       totype
67
68           struct passwd *
69           getpwent_r(struct passwd *pwd, char *buf, int buflen);
70
71       or, better,
72
73           int
74           getpwent_r(struct passwd *pwd, char *buf, int buflen,
75                      FILE **pw_fp);
76

NOTES

78       The  function  getpwent_r() is not really reentrant since it shares the
79       reading position in the stream with all other threads.
80

EXAMPLE

82       #define _GNU_SOURCE
83       #include <pwd.h>
84       #include <stdio.h>
85       #define BUFLEN 4096
86
87       int
88       main(void)
89       {
90           struct passwd pw, *pwp;
91           char buf[BUFLEN];
92           int i;
93
94           setpwent();
95           while (1) {
96               i = getpwent_r(&pw, buf, BUFLEN, &pwp);
97               if (i)
98                   break;
99               printf("%s (%d)\tHOME %s\tSHELL %s\n", pwp->pw_name,
100                      pwp->pw_uid, pwp->pw_dir, pwp->pw_shell);
101           }
102           endpwent();
103           exit(EXIT_SUCCESS);
104       }
105

COLOPHON

111       This  page  is  part of release 3.53 of the Linux man-pages project.  A
112       description of the project, and information about reporting  bugs,  can
113       be found at http://www.kernel.org/doc/man-pages/.
114
115
116
117GNU                               2010-10-21                     GETPWENT_R(3)