1GETPWNAM(3P) POSIX Programmer's Manual GETPWNAM(3P)
2
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
12 getpwnam, getpwnam_r - search user database for a name
13
15 #include <pwd.h>
16 struct passwd *getpwnam(const char *name);
18 int getpwnam_r(const char *name, struct passwd *pwd, char *buffer,
21 size_t bufsize, struct passwd **result);
22
25 The getpwnam() function shall search the user database for an entry
26 with a matching name.
27 The getpwnam() function need not be reentrant. A function that is not
29 required to be reentrant is not required to be thread-safe.
30 Applications wishing to check for error situations should set errno to
32 0 before calling getpwnam(). If getpwnam() returns a null pointer and
33 errno is non-zero, an error occurred.
34 The getpwnam_r() function shall update the passwd structure pointed to
36 by pwd and store a pointer to that structure at the location pointed to
37 by result. The structure shall contain an entry from the user database
38 with a matching name. Storage referenced by the structure is allocated
39 from the memory provided with the buffer parameter, which is bufsize
40 bytes in size. The maximum size needed for this buffer can be deter‐
41 mined with the {_SC_GETPW_R_SIZE_MAX} sysconf() parameter. A NULL
42 pointer shall be returned at the location pointed to by result on error
43 or if the requested entry is not found.
44
46 The getpwnam() function shall return a pointer to a struct passwd with
47 the structure as defined in <pwd.h> with a matching entry if found. A
48 null pointer shall be returned if the requested entry is not found, or
49 an error occurs. On error, errno shall be set to indicate the error.
50 The return value may point to a static area which is overwritten by a
52 subsequent call to getpwent(), getpwnam(), or getpwuid().
53 If successful, the getpwnam_r() function shall return zero; otherwise,
55 an error number shall be returned to indicate the error.
56
58 The getpwnam() and getpwnam_r() functions may fail if:
59 EIO An I/O error has occurred.
61 EINTR A signal was caught during getpwnam().
63 EMFILE {OPEN_MAX} file descriptors are currently open in the calling
65 process.
66 ENFILE The maximum allowable number of files is currently open in the
68 system.
69 The getpwnam_r() function may fail if:
72 ERANGE Insufficient storage was supplied via buffer and bufsize to con‐
74 tain the data to be referenced by the resulting passwd struc‐
75 ture.
76 The following sections are informative.
79
81 Getting an Entry for the Login Name
82 The following example uses the getlogin() function to return the name
83 of the user who logged in; this information is passed to the getpwnam()
84 function to get the user database entry for that user.
85 #include <sys/types.h>
88 #include <pwd.h>
89 #include <unistd.h>
90 #include <stdio.h>
91 #include <stdlib.h>
92 ...
93 char *lgn;
94 struct passwd *pw;
95 ...
96 if ((lgn = getlogin()) == NULL || (pw = getpwnam(lgn)) == NULL) {
97 fprintf(stderr, "Get of user information failed.\n"); exit(1);
98 }
99 ...
100
102 Three names associated with the current process can be determined: get‐
103 pwuid( geteuid()) returns the name associated with the effective user
104 ID of the process; getlogin() returns the name associated with the cur‐
105 rent login activity; and getpwuid( getuid()) returns the name associ‐
106 ated with the real user ID of the process.
107 The getpwnam_r() function is thread-safe and returns values in a user-
109 supplied buffer instead of possibly using a static data area that may
110 be overwritten by each call.
111
113 None.
114
116 None.
117
119 getpwuid(), the Base Definitions volume of IEEE Std 1003.1-2001, <lim‐
120 its.h>, <pwd.h>, <sys/types.h>
121
123 Portions of this text are reprinted and reproduced in electronic form
124 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
125 -- Portable Operating System Interface (POSIX), The Open Group Base
126 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
127 Electrical and Electronics Engineers, Inc and The Open Group. In the
128 event of any discrepancy between this version and the original IEEE and
129 The Open Group Standard, the original IEEE and The Open Group Standard
130 is the referee document. The original Standard can be obtained online
131 at http://www.opengroup.org/unix/online.html .
132IEEE/The Open Group 2003 GETPWNAM(3P)