1GETSPNAM(3)                Linux Programmer's Manual               GETSPNAM(3)
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3
4

NAME

6       getspnam,  getspnam_r,  getspent, getspent_r, setspent, endspent, fget‐
7       spent, fgetspent_r, sgetspent, sgetspent_r, putspent, lckpwdf, ulckpwdf
8       - get shadow password file entry
9

SYNOPSIS

11       /* General shadow password file API */
12       #include <shadow.h>
13
14       struct spwd *getspnam(const char *name);
15       struct spwd *getspent(void);
16
17       void setspent(void);
18       void endspent(void);
19
20       struct spwd *fgetspent(FILE *stream);
21       struct spwd *sgetspent(const char *s);
22
23       int putspent(const struct spwd *p, FILE *stream);
24
25       int lckpwdf(void);
26       int ulckpwdf(void);
27
28       /* GNU extension */
29       #include <shadow.h>
30
31       int getspent_r(struct spwd *spbuf,
32                      char *buf, size_t buflen, struct spwd **spbufp);
33       int getspnam_r(const char *name, struct spwd *spbuf,
34                      char *buf, size_t buflen, struct spwd **spbufp);
35
36       int fgetspent_r(FILE *stream, struct spwd *spbuf,
37                      char *buf, size_t buflen, struct spwd **spbufp);
38       int sgetspent_r(const char *s, struct spwd *spbuf,
39                      char *buf, size_t buflen, struct spwd **spbufp);
40
41   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
42
43       getspent_r(), getspnam_r(), fgetspent_r(), sgetspent_r():
44           Since glibc 2.19:
45               _DEFAULT_SOURCE
46           Glibc 2.19 and earlier:
47               _BSD_SOURCE || _SVID_SOURCE
48

DESCRIPTION

50       Long ago it was considered safe to have encrypted passwords openly vis‐
51       ible in the password file.  When computers got faster  and  people  got
52       more  security-conscious,  this  was  no  longer  acceptable.  Julianne
53       Frances Haugh implemented the shadow password suite that keeps the  en‐
54       crypted  passwords  in  the  shadow  password database (e.g., the local
55       shadow password file /etc/shadow, NIS,  and  LDAP),  readable  only  by
56       root.
57
58       The  functions described below resemble those for the traditional pass‐
59       word database (e.g., see getpwnam(3) and getpwent(3)).
60
61       The getspnam() function returns a pointer to a structure containing the
62       broken-out  fields  of  the record in the shadow password database that
63       matches the username name.
64
65       The getspent() function returns a pointer to  the  next  entry  in  the
66       shadow password database.  The position in the input stream is initial‐
67       ized by setspent().  When done reading, the program may call endspent()
68       so that resources can be deallocated.
69
70       The fgetspent() function is similar to getspent() but uses the supplied
71       stream instead of the one implicitly opened by setspent().
72
73       The sgetspent() function parses the supplied string  s  into  a  struct
74       spwd.
75
76       The putspent() function writes the contents of the supplied struct spwd
77       *p as a text line in the shadow password file format to stream.  String
78       entries with value NULL and numerical entries with value -1 are written
79       as an empty string.
80
81       The lckpwdf() function is intended to protect against multiple simulta‐
82       neous  accesses of the shadow password database.  It tries to acquire a
83       lock, and returns 0 on success, or -1 on  failure  (lock  not  obtained
84       within  15  seconds).  The ulckpwdf() function releases the lock again.
85       Note that there is no protection against direct access  of  the  shadow
86       password file.  Only programs that use lckpwdf() will notice the lock.
87
88       These were the functions that formed the original shadow API.  They are
89       widely available.
90
91   Reentrant versions
92       Analogous to the reentrant functions for the password  database,  glibc
93       also  has  reentrant  functions  for the shadow password database.  The
94       getspnam_r() function is  like  getspnam()  but  stores  the  retrieved
95       shadow  password  structure  in  the  space  pointed to by spbuf.  This
96       shadow password structure  contains  pointers  to  strings,  and  these
97       strings  are stored in the buffer buf of size buflen.  A pointer to the
98       result (in case of success) or NULL (in case no entry was found  or  an
99       error occurred) is stored in *spbufp.
100
101       The  functions getspent_r(), fgetspent_r(), and sgetspent_r() are simi‐
102       larly analogous to their nonreentrant counterparts.
103
104       Some non-glibc systems also have functions with these names, often with
105       different prototypes.
106
107   Structure
108       The shadow password structure is defined in <shadow.h> as follows:
109
110           struct spwd {
111               char *sp_namp;     /* Login name */
112               char *sp_pwdp;     /* Encrypted password */
113               long  sp_lstchg;   /* Date of last change
114                                     (measured in days since
115                                     1970-01-01 00:00:00 +0000 (UTC)) */
116               long  sp_min;      /* Min # of days between changes */
117               long  sp_max;      /* Max # of days between changes */
118               long  sp_warn;     /* # of days before password expires
119                                     to warn user to change it */
120               long  sp_inact;    /* # of days after password expires
121                                     until account is disabled */
122               long  sp_expire;   /* Date when account expires
123                                     (measured in days since
124                                     1970-01-01 00:00:00 +0000 (UTC)) */
125               unsigned long sp_flag;  /* Reserved */
126           };
127

RETURN VALUE

129       The  functions that return a pointer return NULL if no more entries are
130       available or if an error occurs during processing.  The functions which
131       have  int  as the return value return 0 for success and -1 for failure,
132       with errno set to indicate the error.
133
134       For the nonreentrant functions, the return value may  point  to  static
135       area, and may be overwritten by subsequent calls to these functions.
136
137       The  reentrant  functions return zero on success.  In case of error, an
138       error number is returned.
139

ERRORS

141       EACCES The caller does not have permission to access the  shadow  pass‐
142              word file.
143
144       ERANGE Supplied buffer is too small.
145

FILES

147       /etc/shadow
148              local shadow password database file
149
150       /etc/.pwd.lock
151              lock file
152
153       The  include  file  <paths.h>  defines the constant _PATH_SHADOW to the
154       pathname of the shadow password file.
155

ATTRIBUTES

157       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
158       tributes(7).
159
160       ┌──────────────┬───────────────┬───────────────────────────────────────┐
161Interface     Attribute     Value                                 
162       ├──────────────┼───────────────┼───────────────────────────────────────┤
163getspnam()    │ Thread safety │ MT-Unsafe race:getspnam locale        │
164       ├──────────────┼───────────────┼───────────────────────────────────────┤
165getspent()    │ Thread safety │ MT-Unsafe race:getspent race:spentbuf │
166       │              │               │ locale                                │
167       ├──────────────┼───────────────┼───────────────────────────────────────┤
168setspent(),   │ Thread safety │ MT-Unsafe race:getspent locale        │
169endspent(),   │               │                                       │
170getspent_r()  │               │                                       │
171       ├──────────────┼───────────────┼───────────────────────────────────────┤
172fgetspent()   │ Thread safety │ MT-Unsafe race:fgetspent              │
173       ├──────────────┼───────────────┼───────────────────────────────────────┤
174sgetspent()   │ Thread safety │ MT-Unsafe race:sgetspent              │
175       ├──────────────┼───────────────┼───────────────────────────────────────┤
176putspent(),   │ Thread safety │ MT-Safe locale                        │
177getspnam_r(), │               │                                       │
178sgetspent_r() │               │                                       │
179       ├──────────────┼───────────────┼───────────────────────────────────────┤
180lckpwdf(),    │ Thread safety │ MT-Safe                               │
181ulckpwdf(),   │               │                                       │
182fgetspent_r() │               │                                       │
183       └──────────────┴───────────────┴───────────────────────────────────────┘
184       In the above table, getspent in race:getspent signifies that if any  of
185       the  functions  setspent(), getspent(), getspent_r(), or endspent() are
186       used in parallel in different threads of a  program,  then  data  races
187       could occur.
188

CONFORMING TO

190       The  shadow  password database and its associated API are not specified
191       in POSIX.1.  However, many other systems provide a similar API.
192

SEE ALSO

194       getgrnam(3), getpwnam(3), getpwnam_r(3), shadow(5)
195

COLOPHON

197       This page is part of release 5.13 of the Linux  man-pages  project.   A
198       description  of  the project, information about reporting bugs, and the
199       latest    version    of    this    page,    can     be     found     at
200       https://www.kernel.org/doc/man-pages/.
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204GNU                               2021-03-22                       GETSPNAM(3)
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