getpwnam(3)

1GETPWNAM(3)                Linux Programmer's Manual               GETPWNAM(3)
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NAME

6       getpwnam, getpwnam_r, getpwuid, getpwuid_r - get password file entry
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SYNOPSIS

9       #include <sys/types.h>
10       #include <pwd.h>
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12       struct passwd *getpwnam(const char *name);
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14       struct passwd *getpwuid(uid_t uid);
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16       int getpwnam_r(const char *name, struct passwd *pwbuf,
17               char *buf, size_t buflen, struct passwd **pwbufp);
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19       int getpwuid_r(uid_t uid, struct passwd *pwbuf,
20               char *buf, size_t buflen, struct passwd **pwbufp);
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DESCRIPTION

23       The getpwnam() function returns a pointer to a structure containing the
24       broken-out fields of the record in the  password  database  (e.g.,  the
25       local  password  file /etc/passwd, NIS, and LDAP) that matches the user
26       name name.
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28       The getpwuid() function returns a pointer to a structure containing the
29       broken-out  fields  of the record in the password database that matches
30       the user ID uid.
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32       The getpwnam_r() and getpwuid_r() functions obtain  the  same  informa‐
33       tion,  but store the retrieved passwd structure in the space pointed to
34       by pwbuf.  This passwd structure  contains  pointers  to  strings,  and
35       these  strings  are stored in the buffer buf of size buflen.  A pointer
36       to the result (in case of success) or NULL (in case no entry was  found
37       or an error occurred) is stored in *pwbufp.
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39       The passwd structure is defined in <pwd.h> as follows:
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41         struct passwd {
42             char   *pw_name;       /* user name */
43             char   *pw_passwd;     /* user password */
44             uid_t   pw_uid;        /* user ID */
45             gid_t   pw_gid;        /* group ID */
46             char   *pw_gecos;      /* real name */
47             char   *pw_dir;        /* home directory */
48             char   *pw_shell;      /* shell program */
49         };
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51       The  maximum needed size for buf can be found using sysconf(3) with the
52       _SC_GETPW_R_SIZE_MAX parameter.
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RETURN VALUE

55       The getpwnam() and getpwuid() functions return a pointer  to  a  passwd
56       structure,  or  NULL  if  the  matching  entry is not found or an error
57       occurs.  If an error occurs, errno is set appropriately.  If one  wants
58       to  check  errno  after  the  call, it should be set to zero before the
59       call.
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61       The return value may point to static area, and may  be  overwritten  by
62       subsequent calls to getpwent(), getpwnam(), or getpwuid().
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64       The  getpwnam_r() and getpwuid_r() functions return zero on success. In
65       case of error, an error number is returned.
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ERRORS

68       0 or ENOENT or ESRCH or EBADF or EPERM or ...
69              The given name or uid was not found.
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71       EINTR  A signal was caught.
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73       EIO    I/O error.
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75       EMFILE The maximum number (OPEN_MAX) of files was open already  in  the
76              calling process.
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78       ENFILE The maximum number of files was open already in the system.
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80       ENOMEM Insufficient memory to allocate passwd structure.
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82       ERANGE Insufficient buffer space supplied.
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FILES

85       /etc/passwd
86              local password database file
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CONFORMING TO

89       SVr4, 4.3BSD, POSIX.1-2001
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NOTES

92       The  formulation given above under "RETURN VALUE" is from POSIX.1-2001.
93       It does not call "not found" an error, and hence does not specify  what
94       value  errno might have in this situation. But that makes it impossible
95       to recognize errors. One might argue  that  according  to  POSIX  errno
96       should be left unchanged if an entry is not found. Experiments on vari‐
97       ous Unix-like systems show that lots of different values occur in  this
98       situation:  0,  ENOENT,  EBADF,  ESRCH, EWOULDBLOCK, EPERM and probably
99       others.
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101       The pw_dir field contains the name of the initial working directory  of
102       the user.  Login programs use the value of this field to initialize the
103       HOME environment variable for the login  shell.   An  application  that
104       wants  to  determine its user's home directory should inspect the value
105       of HOME (rather than the value getpwuid(getuid())->pw_dir)  since  this
106       allows the user to modify their notion of "the home directory" during a
107       login session.  To determine the (initial) home  directory  of  another
108       user, it is necessary to use getpwnam("username")->pw_dir or similar.
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