calmsacibis995
151 lines
3.6 KiB
Plaintext
151 lines
3.6 KiB
Plaintext
'\"macro stdmacro
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.if n .pH g2.shmget @(#)shmget 41.3 of 5/26/91
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.\" Copyright 1991 UNIX System Laboratories, Inc.
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.\" Copyright 1989, 1990 AT&T
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.nr X
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.if \nX=0 .ds x} shmget 2 "" "\&"
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.if \nX=1 .ds x} shmget 2 ""
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.if \nX=2 .ds x} shmget 2 "" "\&"
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.if \nX=3 .ds x} shmget "" "" "\&"
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.TH \*(x}
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.SH NAME
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\f4shmget\f1 \- get shared memory segment identifier
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.SH SYNOPSIS
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\f4#include <sys/types.h>\f1
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.br
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\f4#include <sys/ipc.h>\f1
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.br
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\f4#include <sys/shm.h>\f1
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.PP
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.nf
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\f4int shmget(key_t key, size_t size, int shmflg);\f1
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.fi
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.SH DESCRIPTION
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\f4shmget\fP
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returns the shared memory identifier associated with
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.IR key .
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.\".P
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.\"If the Enhanced Security Utilities are installed and running,
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.\"the \f2key\fP values are kept on a per-level basis; i.e., \f2shmget\fP
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.\"searches only among \f2key\fP values at the same security level as the
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.\"calling process.
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.PP
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A shared memory identifier and associated data structure and shared memory
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segment of at least
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.I size
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bytes [see
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\f4intro\fP(2)]
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are created for
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.I key
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if one of the following are true:
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.IP
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.I key
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is equal to
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\f4IPC_PRIVATE\f1.
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.IP
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.I key
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does not already have a shared memory identifier associated with it, and
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(\f2shmflg\f4&IPC_CREAT\f1)
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is true.
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.PP
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Upon creation, the contents of the shared memory segment
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are initialized to zero,
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and the data structure associated with the new shared memory
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identifier is initialized as follows:
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.IP
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\f4shm_perm.cuid\f1, \f4shm_perm.uid\f1,
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\f4shm_perm.cgid\f1, and \f4shm_perm.gid\f1
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are set equal to the effective user
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.SM ID
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and effective group
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.SM ID\*S,
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respectively, of the calling process.
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.IP
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The access permission bits of
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\f4shm_perm.mode\f1
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are set equal to the access permission bits of
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.IR shmflg .
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\f4shm_segsz\f1
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is set equal to the value of
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.IR size .
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.IP
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\f4shm_lpid\f1, \f4shm_nattch\f1
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\f4shm_atime\f1, and \f4shm_dtime\f1
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are set equal to 0.
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.IP
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\f4shm_ctime\f1
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is set equal to the current time.
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.IP
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.\"If the Enhanced Security Utilities are installed and running,
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.\"an access control list (ACL) is created for the shared memory segment
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.\"and set empty.
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.PP
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\f4shmget\fP
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fails if one or more of the following are true:
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.TP 15
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\f4EINVAL\fP
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.I size
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is less than the system-imposed minimum
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or greater than the system-imposed maximum.
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.TP
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\f4EACCES\fP
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A shared memory identifier exists for
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.I key
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but operation permission [see
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\f4intro\fP(2)]
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as specified by the low-order 9 bits of
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.I shmflg
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would not be granted.
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.TP
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\f4EINVAL\fP
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A shared memory identifier exists for
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.I key
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but the size of the segment associated with it is less than
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.I size
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and
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.I size
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is not equal to zero.
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.TP
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\f4ENOENT\fP
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A shared memory identifier does not exist for
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.I key
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and
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(\f2shmflg\f4&IPC_CREAT\f1)
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is false.
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.TP
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\f4ENOSPC\fP
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A shared memory identifier is to be created but
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the system-imposed limit on the maximum number of
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allowed shared memory identifiers system wide
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would be exceeded.
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.TP
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\f4ENOMEM\fP
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A shared memory identifier and associated shared memory segment are to be
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created but the amount of available memory is not sufficient to
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fill the request.
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.TP
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\f4EEXIST\fP
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A shared memory identifier exists for
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.I key
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but both
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(\f2shmflg\f4&IPC_CREAT\f1)
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and
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(\f2shmflg\f4&IPC_EXCL\f1)
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are true.
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.br
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.ne 7v
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.SH SEE ALSO
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\f4intro\fP(2), \f4shmctl\fP(2), \f4shmop\fP(2), \f4stdipc\fP(3C), \f4ipcs\fP(1), \f4ipcrm\fP(1).
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.SH "DIAGNOSTICS"
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Upon successful completion,
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a non-negative integer,
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namely a shared memory identifier is returned.
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Otherwise, a value of \-1 is returned and
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\f4errno\fP
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is set to indicate the error.
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.SH NOTES
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The user must explicitly remove shared memory segments
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after the last reference to them has been removed.
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.\" @(#)shmget.2 6.2 of 9/6/83
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.Ee
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