1GETGRGID(P) POSIX Programmer's Manual GETGRGID(P)
2
6 getgrgid, getgrgid_r - get group database entry for a group ID
7
9 #include <grp.h>
10 struct group *getgrgid(gid_t gid);
12 int getgrgid_r(gid_t gid, struct group *grp, char *buffer,
15 size_t bufsize, struct group **result);
16
19 The getgrgid() function shall search the group database for an entry
20 with a matching gid.
21 The getgrgid() function need not be reentrant. A function that is not
23 required to be reentrant is not required to be thread-safe.
24 The getgrgid_r() function shall update the group structure pointed to
26 by grp and store a pointer to that structure at the location pointed to
27 by result. The structure shall contain an entry from the group database
28 with a matching gid. Storage referenced by the group structure is allo‐
29 cated from the memory provided with the buffer parameter, which is buf‐
30 size bytes in size. The maximum size needed for this buffer can be
31 determined with the {_SC_GETGR_R_SIZE_MAX} sysconf() parameter. A NULL
32 pointer shall be returned at the location pointed to by result on error
33 or if the requested entry is not found.
34
36 Upon successful completion, getgrgid() shall return a pointer to a
37 struct group with the structure defined in <grp.h> with a matching
38 entry if one is found. The getgrgid() function shall return a null
39 pointer if either the requested entry was not found, or an error
40 occurred. On error, errno shall be set to indicate the error.
41 The return value may point to a static area which is overwritten by a
43 subsequent call to getgrent(), getgrgid(), or getgrnam().
44 If successful, the getgrgid_r() function shall return zero; otherwise,
46 an error number shall be returned to indicate the error.
47
49 The getgrgid() and getgrgid_r() functions may fail if:
50 EIO An I/O error has occurred.
52 EINTR A signal was caught during getgrgid().
54 EMFILE {OPEN_MAX} file descriptors are currently open in the calling
56 process.
57 ENFILE The maximum allowable number of files is currently open in the
59 system.
60 The getgrgid_r() function may fail if:
63 ERANGE Insufficient storage was supplied via buffer and bufsize to con‐
65 tain the data to be referenced by the resulting group structure.
66 The following sections are informative.
69
71 Finding an Entry in the Group Database
72 The following example uses getgrgid() to search the group database for
73 a group ID that was previously stored in a stat structure, then prints
74 out the group name if it is found. If the group is not found, the pro‐
75 gram prints the numeric value of the group for the entry.
76 #include <sys/types.h>
79 #include <grp.h>
80 #include <stdio.h>
81 ...
82 struct stat statbuf;
83 struct group *grp;
84 ...
85 if ((grp = getgrgid(statbuf.st_gid)) != NULL)
86 printf(" %-8.8s", grp->gr_name);
87 else
88 printf(" %-8d", statbuf.st_gid);
89 ...
90
92 Applications wishing to check for error situations should set errno to
93 0 before calling getgrgid(). If errno is set on return, an error
94 occurred.
95 The getgrgid_r() function is thread-safe and shall return values in a
97 user-supplied buffer instead of possibly using a static data area that
98 may be overwritten by each call.
99
101 None.
102
104 None.
105
107 endgrent() , getgrnam() , the Base Definitions volume of
108 IEEE Std 1003.1-2001, <grp.h>, <limits.h>, <sys/types.h>
109
111 Portions of this text are reprinted and reproduced in electronic form
112 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
113 -- Portable Operating System Interface (POSIX), The Open Group Base
114 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
115 Electrical and Electronics Engineers, Inc and The Open Group. In the
116 event of any discrepancy between this version and the original IEEE and
117 The Open Group Standard, the original IEEE and The Open Group Standard
118 is the referee document. The original Standard can be obtained online
119 at http://www.opengroup.org/unix/online.html .
120IEEE/The Open Group 2003 GETGRGID(P)