man3/getpwent.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\"
  30 .\" Modified Sat Jul 24 19:22:14 1993 by Rik Faith (faith@cs.unc.edu)
  31 .\" Modified Mon May 27 21:37:47 1996 by Martin Schulze (joey@linux.de)
  32 .\"
  33 .TH GETPWENT 3  2016-03-15 "GNU" "Linux Programmer's Manual"
  34 .SH NAME
  35 getpwent, setpwent, endpwent \- get password file entry
  36 .SH SYNOPSIS
  37 .nf
  38 .B #include <sys/types.h>
  39 .B #include <pwd.h>
  40 .PP
  41 .B struct passwd *getpwent(void);
  42 .PP
  43 .B void setpwent(void);
  44 .PP
  45 .B void endpwent(void);
  46 .fi
  47 .PP
  48 .in -4n
  49 Feature Test Macro Requirements for glibc (see
  50 .BR feature_test_macros (7)):
  51 .in
  52 .PP
  53 .ad l
  54 .BR getpwent (),
  55 .BR setpwent (),
  56 .BR endpwent ():
  57 .RS 4
  58 _XOPEN_SOURCE\ >=\ 500
  59 .\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  60     || /* Glibc since 2.19: */ _DEFAULT_SOURCE
  61     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  62 .RE
  63 .ad b
  64 .SH DESCRIPTION
  65 The
  66 .BR getpwent ()
  67 function returns a pointer to a structure containing
  68 the broken-out fields of a record from the password database
  69 (e.g., the local password file
  70 .IR /etc/passwd ,
  71 NIS, and LDAP).
  72 The first time
  73 .BR getpwent ()
  74 is called, it returns the first entry; thereafter, it returns successive
  75 entries.
  76 .PP
  77 The
  78 .BR setpwent ()
  79 function rewinds to the beginning
  80 of the password database.
  81 .PP
  82 The
  83 .BR endpwent ()
  84 function is used to close the password database
  85 after all processing has been performed.
  86 .PP
  87 The \fIpasswd\fP structure is defined in \fI<pwd.h>\fP as follows:
  88 .PP
  89 .in +4n
  90 .nf
  91 struct passwd {
  92     char   *pw_name;       /* username */
  93     char   *pw_passwd;     /* user password */
  94     uid_t   pw_uid;        /* user ID */
  95     gid_t   pw_gid;        /* group ID */
  96     char   *pw_gecos;      /* user information */
  97     char   *pw_dir;        /* home directory */
  98     char   *pw_shell;      /* shell program */
  99 };
 100 .fi
 101 .in
 102 .PP
 103 For more information about the fields of this structure, see
 104 .BR passwd (5).
 105 .SH RETURN VALUE
 106 The
 107 .BR getpwent ()
 108 function returns a pointer to a
 109 .I passwd
 110 structure, or NULL if
 111 there are no more entries or an error occurred.
 112 If an error occurs,
 113 .I errno
 114 is set appropriately.
 115 If one wants to check
 116 .I errno
 117 after the call, it should be set to zero before the call.
 118 .PP
 119 The return value may point to a static area, and may be overwritten
 120 by subsequent calls to
 121 .BR getpwent (),
 122 .BR getpwnam (3),
 123 or
 124 .BR getpwuid (3).
 125 (Do not pass the returned pointer to
 126 .BR free (3).)
 127 .SH ERRORS
 128 .TP
 129 .B EINTR
 130 A signal was caught; see
 131 .BR signal (7).
 132 .TP
 133 .B EIO
 134 I/O error.
 135 .TP
 136 .B EMFILE
 137 The per-process limit on the number of open file descriptors has been reached.
 138 .TP
 139 .B ENFILE
 140 The system-wide limit on the total number of open files has been reached.
 141 .TP
 142 .B ENOMEM
 143 .\" not in POSIX
 144 Insufficient memory to allocate
 145 .I passwd
 146 structure.
 147 .\" to allocate the passwd structure, or to allocate buffers
 148 .TP
 149 .B ERANGE
 150 Insufficient buffer space supplied.
 151 .SH FILES
 152 .TP
 153 .I /etc/passwd
 154 local password database file
 155 .SH ATTRIBUTES
 156 For an explanation of the terms used in this section, see
 157 .BR attributes (7).
 158 .TS
 159 allbox;
 160 lbw11 lb lb
 161 l l l.
 162 Interface       Attribute       Value
 163 T{
 164 .BR getpwent ()
 165 T}      Thread safety   T{
 166 MT-Unsafe race:pwent
 167 .br
 168 race:pwentbuf locale
 169 T}
 170 T{
 171 .BR setpwent (),
 172 .br
 173 .BR endpwent ()
 174 T}      Thread safety   MT-Unsafe race:pwent locale
 175 .TE
 176 .sp 1
 177 In the above table,
 178 .I pwent
 179 in
 180 .I race:pwent
 181 signifies that if any of the functions
 182 .BR setpwent (),
 183 .BR getpwent (),
 184 or
 185 .BR endpwent ()
 186 are used in parallel in different threads of a program,
 187 then data races could occur.
 188 .SH CONFORMING TO
 189 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
 190 The
 191 .I pw_gecos
 192 field is not specified in POSIX, but is present on most implementations.
 193 .SH SEE ALSO
 194 .BR fgetpwent (3),
 195 .BR getpw (3),
 196 .BR getpwent_r (3),
 197 .BR getpwnam (3),
 198 .BR getpwuid (3),
 199 .BR putpwent (3),
 200 .BR passwd (5)