1SEM_INIT(3P) POSIX Programmer's Manual SEM_INIT(3P)
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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.
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13 sem_init — initialize an unnamed semaphore
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16 #include <semaphore.h>
17 int sem_init(sem_t *sem, int pshared, unsigned value);
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21 The sem_init() function shall initialize the unnamed semaphore referred
22 to by sem. The value of the initialized semaphore shall be value.
23 Following a successful call to sem_init(), the semaphore may be used in
24 subsequent calls to sem_wait(), sem_timedwait(), sem_trywait(),
25 sem_post(), and sem_destroy(). This semaphore shall remain usable
26 until the semaphore is destroyed.
27 If the pshared argument has a non-zero value, then the semaphore is
29 shared between processes; in this case, any process that can access the
30 semaphore sem can use sem for performing sem_wait(), sem_timedwait(),
31 sem_trywait(), sem_post(), and sem_destroy() operations.
32 Only sem itself may be used for performing synchronization. The result
34 of referring to copies of sem in calls to sem_wait(), sem_timedwait(),
35 sem_trywait(), sem_post(), and sem_destroy() is undefined.
36 If the pshared argument is zero, then the semaphore is shared between
38 threads of the process; any thread in this process can use sem for per‐
39 forming sem_wait(), sem_timedwait(), sem_trywait(), sem_post(), and
40 sem_destroy() operations. The use of the semaphore by threads other
41 than those created in the same process is undefined.
42 Attempting to initialize an already initialized semaphore results in
44 undefined behavior.
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47 Upon successful completion, the sem_init() function shall initialize
48 the semaphore in sem and return 0. Otherwise, it shall return −1 and
49 set errno to indicate the error.
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52 The sem_init() function shall fail if:
53 EINVAL The value argument exceeds {SEM_VALUE_MAX}.
55 ENOSPC A resource required to initialize the semaphore has been
57 exhausted, or the limit on semaphores ({SEM_NSEMS_MAX}) has been
58 reached.
59 EPERM The process lacks appropriate privileges to initialize the sema‐
61 phore.
62 The following sections are informative.
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66 None.
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69 None.
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72 None.
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75 None.
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78 sem_destroy(), sem_post(), sem_timedwait(), sem_trywait()
79 The Base Definitions volume of POSIX.1‐2008, <semaphore.h>
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83 Portions of this text are reprinted and reproduced in electronic form
84 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
85 -- Portable Operating System Interface (POSIX), The Open Group Base
86 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
87 cal and Electronics Engineers, Inc and The Open Group. (This is
88 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
89 event of any discrepancy between this version and the original IEEE and
90 The Open Group Standard, the original IEEE and The Open Group Standard
91 is the referee document. The original Standard can be obtained online
92 at http://www.unix.org/online.html .
93 Any typographical or formatting errors that appear in this page are
95 most likely to have been introduced during the conversion of the source
96 files to man page format. To report such errors, see https://www.ker‐
97 nel.org/doc/man-pages/reporting_bugs.html .
98IEEE/The Open Group 2013 SEM_INIT(3P)