1SHM_UNLINK(3P) POSIX Programmer's Manual SHM_UNLINK(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 shm_unlink — remove a shared memory object (REALTIME)
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15 #include <sys/mman.h>
16 int shm_unlink(const char *name);
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20 The shm_unlink() function shall remove the name of the shared memory
21 object named by the string pointed to by name.
22 If one or more references to the shared memory object exist when the
24 object is unlinked, the name shall be removed before shm_unlink()
25 returns, but the removal of the memory object contents shall be post‐
26 poned until all open and map references to the shared memory object
27 have been removed.
28 Even if the object continues to exist after the last shm_unlink(), re‐
30 use of the name shall subsequently cause shm_open() to behave as if no
31 shared memory object of this name exists (that is, shm_open() will fail
32 if O_CREAT is not set, or will create a new shared memory object if
33 O_CREAT is set).
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36 Upon successful completion, a value of zero shall be returned. Other‐
37 wise, a value of -1 shall be returned and errno set to indicate the
38 error. If -1 is returned, the named shared memory object shall not be
39 changed by this function call.
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42 The shm_unlink() function shall fail if:
43 EACCES Permission is denied to unlink the named shared memory object.
45 ENOENT The named shared memory object does not exist.
47 The shm_unlink() function may fail if:
49 ENAMETOOLONG
51 The length of the name argument exceeds {_POSIX_PATH_MAX} on
52 systems that do not support the XSI option or exceeds
53 {_XOPEN_PATH_MAX} on XSI systems, or has a pathname component
54 that is longer than {_POSIX_NAME_MAX} on systems that do not
55 support the XSI option or longer than {_XOPEN_NAME_MAX} on XSI
56 systems. A call to shm_unlink() with a name argument that con‐
57 tains the same shared memory object name as was previously used
58 in a successful shm_open() call shall not give an [ENAMETOOLONG]
59 error.
60 The following sections are informative.
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64 None.
65
67 Names of memory objects that were allocated with open() are deleted
68 with unlink() in the usual fashion. Names of memory objects that were
69 allocated with shm_open() are deleted with shm_unlink(). Note that the
70 actual memory object is not destroyed until the last close and unmap on
71 it have occurred if it was already in use.
72
74 None.
75
77 A future version might require the shm_open() and shm_unlink() func‐
78 tions to have semantics similar to normal file system operations.
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81 close(), mmap(), munmap(), shmat(), shmctl(), shmdt(), shm_open()
82 The Base Definitions volume of POSIX.1‐2017, <sys_mman.h>
84
86 Portions of this text are reprinted and reproduced in electronic form
87 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
88 table Operating System Interface (POSIX), The Open Group Base Specifi‐
89 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
90 Electrical and Electronics Engineers, Inc and The Open Group. In the
91 event of any discrepancy between this version and the original IEEE and
92 The Open Group Standard, the original IEEE and The Open Group Standard
93 is the referee document. The original Standard can be obtained online
94 at http://www.opengroup.org/unix/online.html .
95 Any typographical or formatting errors that appear in this page are
97 most likely to have been introduced during the conversion of the source
98 files to man page format. To report such errors, see https://www.ker‐
99 nel.org/doc/man-pages/reporting_bugs.html .
100IEEE/The Open Group 2017 SHM_UNLINK(3P)