1GETGRGID(3P) POSIX Programmer's Manual GETGRGID(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 getgrgid, getgrgid_r - get group database entry for a group ID
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15 #include <grp.h>
16 struct group *getgrgid(gid_t gid);
18 int getgrgid_r(gid_t gid, struct group *grp, char *buffer,
21 size_t bufsize, struct group **result);
22
25 The getgrgid() function shall search the group database for an entry
26 with a matching gid.
27 The getgrgid() function need not be reentrant. A function that is not
29 required to be reentrant is not required to be thread-safe.
30 The getgrgid_r() function shall update the group structure pointed to
32 by grp and store a pointer to that structure at the location pointed to
33 by result. The structure shall contain an entry from the group database
34 with a matching gid. Storage referenced by the group structure is allo‐
35 cated from the memory provided with the buffer parameter, which is buf‐
36 size bytes in size. The maximum size needed for this buffer can be
37 determined with the {_SC_GETGR_R_SIZE_MAX} sysconf() parameter. A NULL
38 pointer shall be returned at the location pointed to by result on error
39 or if the requested entry is not found.
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42 Upon successful completion, getgrgid() shall return a pointer to a
43 struct group with the structure defined in <grp.h> with a matching
44 entry if one is found. The getgrgid() function shall return a null
45 pointer if either the requested entry was not found, or an error
46 occurred. On error, errno shall be set to indicate the error.
47 The return value may point to a static area which is overwritten by a
49 subsequent call to getgrent(), getgrgid(), or getgrnam().
50 If successful, the getgrgid_r() function shall return zero; otherwise,
52 an error number shall be returned to indicate the error.
53
55 The getgrgid() and getgrgid_r() functions may fail if:
56 EIO An I/O error has occurred.
58 EINTR A signal was caught during getgrgid().
60 EMFILE {OPEN_MAX} file descriptors are currently open in the calling
62 process.
63 ENFILE The maximum allowable number of files is currently open in the
65 system.
66 The getgrgid_r() function may fail if:
69 ERANGE Insufficient storage was supplied via buffer and bufsize to con‐
71 tain the data to be referenced by the resulting group structure.
72 The following sections are informative.
75
77 Finding an Entry in the Group Database
78 The following example uses getgrgid() to search the group database for
79 a group ID that was previously stored in a stat structure, then prints
80 out the group name if it is found. If the group is not found, the pro‐
81 gram prints the numeric value of the group for the entry.
82 #include <sys/types.h>
85 #include <grp.h>
86 #include <stdio.h>
87 ...
88 struct stat statbuf;
89 struct group *grp;
90 ...
91 if ((grp = getgrgid(statbuf.st_gid)) != NULL)
92 printf(" %-8.8s", grp->gr_name);
93 else
94 printf(" %-8d", statbuf.st_gid);
95 ...
96
98 Applications wishing to check for error situations should set errno to
99 0 before calling getgrgid(). If errno is set on return, an error
100 occurred.
101 The getgrgid_r() function is thread-safe and shall return values in a
103 user-supplied buffer instead of possibly using a static data area that
104 may be overwritten by each call.
105
107 None.
108
110 None.
111
113 endgrent(), getgrnam(), the Base Definitions volume of
114 IEEE Std 1003.1-2001, <grp.h>, <limits.h>, <sys/types.h>
115
117 Portions of this text are reprinted and reproduced in electronic form
118 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
119 -- Portable Operating System Interface (POSIX), The Open Group Base
120 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
121 Electrical and Electronics Engineers, Inc and The Open Group. In the
122 event of any discrepancy between this version and the original IEEE and
123 The Open Group Standard, the original IEEE and The Open Group Standard
124 is the referee document. The original Standard can be obtained online
125 at http://www.opengroup.org/unix/online.html .
126IEEE/The Open Group 2003 GETGRGID(3P)