1ENDPWENT(3P)               POSIX Programmer's Manual              ENDPWENT(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
10

NAME

12       endpwent, getpwent, setpwent — user database functions
13

SYNOPSIS

15       #include <pwd.h>
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17       void endpwent(void);
18       struct passwd *getpwent(void);
19       void setpwent(void);
20

DESCRIPTION

22       These functions shall retrieve information about users.
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24       The getpwent() function shall return a pointer to a structure  contain‐
25       ing  the broken-out fields of an entry in the user database. Each entry
26       in the user database contains a passwd structure. If the user  database
27       is not already open, getpwent() shall open it and return a pointer to a
28       passwd structure containing the first entry  in  the  database.  There‐
29       after,  it  shall return a pointer to a passwd structure containing the
30       next entry in the user database. Successive calls can be used to search
31       the entire user database.
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33       If  an  end-of-file  or  an error is encountered on reading, getpwent()
34       shall return a null pointer.
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36       An implementation that provides extended security controls  may  impose
37       further implementation-defined restrictions on accessing the user data‐
38       base. In particular, the system may deny the existence of some  or  all
39       of the user database entries associated with users other than the call‐
40       er.
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42       The setpwent() function shall rewind the user database so that the next
43       getpwent() call returns the first entry, allowing repeated searches.
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45       The endpwent() function shall close the user database.
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47       The setpwent() and endpwent() functions shall not change the setting of
48       errno if successful.
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50       On error, the setpwent() and endpwent() functions shall  set  errno  to
51       indicate the error.
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53       Since  no value is returned by the setpwent() and endpwent() functions,
54       an application wishing to check for error situations should  set  errno
55       to 0, then call the function, then check errno.
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57       These functions need not be thread-safe.
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RETURN VALUE

60       On successful completion, getpwent() shall return a pointer to a passwd
61       structure. On end-of-file, getpwent() shall return a null  pointer  and
62       shall  not  change  the  setting  of errno.  On error, getpwent() shall
63       return a null pointer and errno shall be set to indicate the error.
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65       The application shall not modify the  structure  to  which  the  return
66       value  points,  nor any storage areas pointed to by pointers within the
67       structure. The returned pointer, and  pointers  within  the  structure,
68       might  be  invalidated  or  the structure or the storage areas might be
69       overwritten by a subsequent call to getpwuid(),  getpwnam(),  or  getp‐
70       went().  The returned pointer, and pointers within the structure, might
71       also be invalidated if the calling thread is terminated.
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ERRORS

74       These functions may fail if:
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76       EINTR  A signal was caught during the operation.
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78       EIO    An I/O error has occurred.
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80       In addition, getpwent() and setpwent() may fail if:
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82       EMFILE All file descriptors available  to  the  process  are  currently
83              open.
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85       ENFILE The  maximum  allowable number of files is currently open in the
86              system.
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88       The following sections are informative.
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EXAMPLES

91   Searching the User Database
92       The following example uses the getpwent() function  to  get  successive
93       entries in the user database, returning a pointer to a passwd structure
94       that contains information about  each  user.  The  call  to  endpwent()
95       closes the user database and cleans up.
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97
98           #include <pwd.h>
99           #include <stdio.h>
100
101           void printname(uid_t uid)
102           {
103               struct passwd *pwd;
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105               setpwent();
106               while((pwd = getpwent()) != NULL) {
107                   if (pwd->pw_uid == uid) {
108                       printf("name=%s\n",pwd->pw_name);
109                       break;
110                   }
111               }
112               endpwent();
113           }
114

APPLICATION USAGE

116       These  functions  are provided due to their historical usage.  Applica‐
117       tions should avoid dependencies on fields  in  the  password  database,
118       whether the database is a single file, or where in the file system name
119       space the database resides. Applications should use getpwuid() whenever
120       possible because it avoids these dependencies.
121

RATIONALE

123       None.
124

FUTURE DIRECTIONS

126       None.
127

SEE ALSO

129       endgrent(), getlogin(), getpwnam(), getpwuid()
130
131       The Base Definitions volume of POSIX.1‐2017, <pwd.h>
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134       Portions  of  this text are reprinted and reproduced in electronic form
135       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
136       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
137       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
138       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
139       event of any discrepancy between this version and the original IEEE and
140       The  Open Group Standard, the original IEEE and The Open Group Standard
141       is the referee document. The original Standard can be  obtained  online
142       at http://www.opengroup.org/unix/online.html .
143
144       Any  typographical  or  formatting  errors that appear in this page are
145       most likely to have been introduced during the conversion of the source
146       files  to  man page format. To report such errors, see https://www.ker
147       nel.org/doc/man-pages/reporting_bugs.html .
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151IEEE/The Open Group                  2017                         ENDPWENT(3P)
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