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
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SYNOPSIS

9       #include <pwd.h>
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11       int getpwent_r(struct passwd *pwbuf, char *buf,
12                      size_t buflen, struct passwd **pwbufp);
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14       int fgetpwent_r(FILE *fp, struct passwd *pwbuf, char *buf,
15                       size_t buflen, struct passwd **pwbufp);
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17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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19       getpwent_r(), _BSD_SOURCE || _SVID_SOURCE
20       fgetpwent_r(): _SVID_SOURCE
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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:
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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;     /* real name */
36               char    *pw_dir;       /* home directory */
37               char    *pw_shell;     /* shell program */
38           };
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40       The nonreentrant functions return a pointer to  static  storage,  where
41       this  static  storage contains further pointers to user name, password,
42       gecos  field,  home  directory  and  shell.   The  reentrant  functions
43       described here return all of that in caller-provided buffers.  First of
44       all there is the buffer pwbuf that can hold a struct passwd.  And  next
45       the  buffer  buf  of size buflen that can hold additional strings.  The
46       result of these functions, the struct passwd read from the  stream,  is
47       stored  in  the  provided  buffer  *pwbuf, and a pointer to this struct
48       passwd is returned in *pwbufp.
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RETURN VALUE

51       On success, these functions return 0 and *pwbufp is a  pointer  to  the
52       struct  passwd.   On  error,  these functions return an error value and
53       *pwbufp is NULL.
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ERRORS

56       ENOENT No more entries.
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58       ERANGE Insufficient buffer space supplied.  Try again with larger  buf‐
59              fer.
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CONFORMING TO

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

76       The  function  getpwent_r() is not really reentrant since it shares the
77       reading position in the stream with all other threads.
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EXAMPLE

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

109       This  page  is  part of release 3.25 of the Linux man-pages project.  A
110       description of the project, and information about reporting  bugs,  can
111       be found at http://www.kernel.org/doc/man-pages/.
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115GNU                               2007-07-26                     GETPWENT_R(3)