Originální popis anglicky:
getgrgid, getgrgid_r - get group database entry for a group ID
Návod, kniha: POSIX Programmer's Manual
#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);
The
getgrgid() function shall search the group database for an entry with
a matching
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 structure 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.
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.
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.
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);
...
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.
None.
None.
endgrent() ,
getgrnam() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<grp.h>,
<limits.h>,
<sys/types.h>
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
.
