mirror of https://github.com/mkerrisk/man-pages
143 lines
4.5 KiB
Plaintext
143 lines
4.5 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "GETGRGID" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" getgrgid
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.SH NAME
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getgrgid, getgrgid_r \- get group database entry for a group ID
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.SH SYNOPSIS
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.LP
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\fB#include <grp.h>
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.br
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.sp
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struct group *getgrgid(gid_t\fP \fIgid\fP\fB);
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.br
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\fP
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.LP
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\fBint getgrgid_r(gid_t\fP \fIgid\fP\fB, struct group *\fP\fIgrp\fP\fB,
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char
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*\fP\fIbuffer\fP\fB,
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.br
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\ \ \ \ \ \ size_t\fP \fIbufsize\fP\fB, struct group **\fP\fIresult\fP\fB);
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\fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIgetgrgid\fP() function shall search the group database for
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an entry with a matching \fIgid\fP.
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.LP
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The \fIgetgrgid\fP() function need not be reentrant. A function that
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is not required to be reentrant is not required to be
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thread-safe.
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.LP
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The \fIgetgrgid_r\fP() function shall update the \fBgroup\fP structure
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pointed to by \fIgrp\fP and store a pointer to that
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structure at the location pointed to by \fIresult\fP. The structure
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shall contain an entry from the group database with a matching
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\fIgid\fP. Storage referenced by the group structure is allocated
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from the memory provided with the \fIbuffer\fP parameter, which
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is \fIbufsize\fP bytes in size. The maximum size needed for this buffer
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can be determined with the {_SC_GETGR_R_SIZE_MAX} \fIsysconf\fP()
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parameter. A NULL pointer shall be returned at the location pointed
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to by
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\fIresult\fP on error or if the requested entry is not found.
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.SH RETURN VALUE
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.LP
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Upon successful completion, \fIgetgrgid\fP() shall return a pointer
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to a \fBstruct group\fP with the structure defined in \fI<grp.h>\fP
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with a matching entry if one is found. The \fIgetgrgid\fP() function
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shall
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return a null pointer if either the requested entry was not found,
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or an error occurred. On error, \fIerrno\fP shall be set to
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indicate the error.
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.LP
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The return value may point to a static area which is overwritten by
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a subsequent call to \fIgetgrent\fP(), \fIgetgrgid\fP(), or \fIgetgrnam\fP().
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.LP
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If successful, the \fIgetgrgid_r\fP() function shall return zero;
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otherwise, an error number shall be returned to indicate the
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error.
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.SH ERRORS
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.LP
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The \fIgetgrgid\fP() and \fIgetgrgid_r\fP() functions may fail if:
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.TP 7
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.B EIO
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An I/O error has occurred.
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.TP 7
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.B EINTR
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A signal was caught during \fIgetgrgid\fP().
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.TP 7
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.B EMFILE
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{OPEN_MAX} file descriptors are currently open in the calling process.
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.TP 7
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.B ENFILE
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The maximum allowable number of files is currently open in the system.
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.sp
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.LP
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The \fIgetgrgid_r\fP() function may fail if:
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.TP 7
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.B ERANGE
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Insufficient storage was supplied via \fIbuffer\fP and \fIbufsize\fP
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to contain the data to be referenced by the resulting
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\fBgroup\fP structure.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.SS Finding an Entry in the Group Database
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.LP
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The following example uses \fIgetgrgid\fP() to search the group database
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for a group ID that was previously stored in a
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\fBstat\fP structure, then prints out the group name if it is found.
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If the group is not found, the program prints the numeric
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value of the group for the entry.
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.sp
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.RS
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.nf
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\fB#include <sys/types.h>
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#include <grp.h>
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#include <stdio.h>
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\&...
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struct stat statbuf;
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struct group *grp;
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\&...
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if ((grp = getgrgid(statbuf.st_gid)) != NULL)
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printf(" %-8.8s", grp->gr_name);
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else
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printf(" %-8d", statbuf.st_gid);
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\&...
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\fP
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.fi
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.RE
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.SH APPLICATION USAGE
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.LP
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Applications wishing to check for error situations should set \fIerrno\fP
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to 0 before calling \fIgetgrgid\fP(). If
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\fIerrno\fP is set on return, an error occurred.
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.LP
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The \fIgetgrgid_r\fP() function is thread-safe and shall return values
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in a user-supplied buffer instead of possibly using a
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static data area that may be overwritten by each call.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIendgrent\fP() , \fIgetgrnam\fP() , the Base Definitions volume
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of
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IEEE\ Std\ 1003.1-2001, \fI<grp.h>\fP, \fI<limits.h>\fP, \fI<sys/types.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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