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GETGRGID(P) GETGRGID(P)
NAME
getgrgid, getgrgid_r - get group database entry for a group ID
SYNOPSIS
#include <grp.h>
struct group *getgrgid(gid_t gid);
int getgrgid_r(gid_t gid, struct group *grp, char *buffer,
size_t bufsize, struct group **result);
DESCRIPTION
The getgrgid() function shall search the group database for an entry with a match-
ing gid.
The getgrgid() function need not be reentrant. A function that is not required to
be reentrant is not required to be thread-safe.
The getgrgid_r() function shall update the group structure pointed to by grp and
store a pointer to that structure at the location pointed to by result. The struc-
ture shall contain an entry from the group database with a matching gid. Storage
referenced by the group structure is allocated from the memory provided with the
buffer parameter, which is bufsize bytes in size. The maximum size needed for this
buffer can be determined with the {_SC_GETGR_R_SIZE_MAX} sysconf() parameter. A
NULL pointer shall be returned at the location pointed to by result on error or if
the requested entry is not found.
RETURN VALUE
Upon successful completion, getgrgid() shall return a pointer to a struct group
with the structure defined in <grp.h> with a matching entry if one is found. The
getgrgid() function shall return a null pointer if either the requested entry was
not found, or an error occurred. On error, errno shall be set to indicate the
error.
The return value may point to a static area which is overwritten by a subsequent
call to getgrent(), getgrgid(), or getgrnam().
If successful, the getgrgid_r() function shall return zero; otherwise, an error
number shall be returned to indicate the error.
ERRORS
The getgrgid() and getgrgid_r() functions may fail if:
EIO An I/O error has occurred.
EINTR A signal was caught during getgrgid().
EMFILE {OPEN_MAX} file descriptors are currently open in the calling process.
ENFILE The maximum allowable number of files is currently open in the system.
The getgrgid_r() function may fail if:
ERANGE Insufficient storage was supplied via buffer and bufsize to contain the data
to be referenced by the resulting group structure.
The following sections are informative.
EXAMPLES
Finding an Entry in the Group Database
The following example uses getgrgid() to search the group database for a group ID
that was previously stored in a stat structure, then prints out the group name if
it is found. If the group is not found, the program prints the numeric value of
the group for the entry.
#include <sys/types.h>
#include <grp.h>
#include <stdio.h>
...
struct stat statbuf;
struct group *grp;
...
if ((grp = getgrgid(statbuf.st_gid)) != NULL)
printf(" %-8.8s", grp->gr_name);
else
printf(" %-8d", statbuf.st_gid);
...
APPLICATION USAGE
Applications wishing to check for error situations should set errno to 0 before
calling getgrgid(). If errno is set on return, an error occurred.
The getgrgid_r() function is thread-safe and shall return values in a user-supplied
buffer instead of possibly using a static data area that may be overwritten by each
call.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
endgrent() , getgrnam() , the Base Definitions volume of IEEE Std 1003.1-2001,
<grp.h>, <limits.h>, <sys/types.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating
System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C)
2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The
Open Group. In the event of any discrepancy between this version and the original
IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is
the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
POSIX 2003 GETGRGID(P)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache/1.3.41 (Unix) PHP/5.2.5 mod_perl/1.30 mod_gzip/1.3.26.1a
Under GNU General Public License
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