projects / thirdparty / man-pages.git / blame
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1 | '\" t |
| 2 | .\" Hey Emacs! This file is -*- nroff -*- source. | |
| 3 | .\" | |
| c11b1abf | 4 | .\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com> |
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5 | .\" |
| 6 | .\" Permission is granted to make and distribute verbatim copies of this | |
| 7 | .\" manual provided the copyright notice and this permission notice are | |
| 8 | .\" preserved on all copies. | |
| 9 | .\" | |
| 10 | .\" Permission is granted to copy and distribute modified versions of this | |
| 11 | .\" manual under the conditions for verbatim copying, provided that the | |
| 12 | .\" entire resulting derived work is distributed under the terms of a | |
| 13 | .\" permission notice identical to this one. | |
| c13182ef | 14 | .\" |
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15 | .\" Since the Linux kernel and libraries are constantly changing, this |
| 16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
| 17 | .\" responsibility for errors or omissions, or for damages resulting from | |
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18 | .\" the use of the information contained herein. The author(s) may not |
| 19 | .\" have taken the same level of care in the production of this manual, | |
| 20 | .\" which is licensed free of charge, as they might when working | |
| 21 | .\" professionally. | |
| c13182ef | 22 | .\" |
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23 | .\" Formatted or processed versions of this manual, if unaccompanied by |
| 24 | .\" the source, must acknowledge the copyright and authors of this work. | |
| 25 | .\" | |
| d9343c5c | 26 | .TH SEM_POST 3 2006-03-25 "Linux" "Linux Programmer's Manual" |
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27 | .SH NAME |
| 28 | sem_post \- unlock a semaphore | |
| 29 | .SH SYNOPSIS | |
| 30 | .nf | |
| 31 | .B #include <semaphore.h> | |
| 32 | .sp | |
| 33 | .BI "int sem_post(sem_t *" sem ); | |
| 34 | .fi | |
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35 | .sp |
| 36 | Link with \fI\-lrt\fP or \fI\-pthread\fP. | |
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37 | .SH DESCRIPTION |
| 38 | .BR sem_post () | |
| 39 | increments (unlocks) the semaphore pointed to by | |
| 40 | .IR sem . | |
| 41 | If the semaphore's value consequently becomes greater than zero, | |
| c13182ef | 42 | then another process or thread blocked in a |
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43 | .BR sem_wait (3) |
| 44 | call will be woken up and proceed to lock the semaphore. | |
| 45 | .SH RETURN VALUE | |
| 46 | .BR sem_post () | |
| c13182ef | 47 | returns 0 on success; |
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48 | on error, the value of the semaphore is left unchanged, |
| 49 | \-1 is returned, and | |
| c13182ef | 50 | .I errno |
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51 | is set to indicate the error. |
| 52 | .SH ERRORS | |
| 53 | .TP | |
| 54 | .B EINVAL | |
| 55 | .I sem | |
| 56 | is not a valid semaphore. | |
| 57 | .SH CONFORMING TO | |
| 58 | POSIX.1-2001. | |
| 59 | .SH NOTES | |
| 60 | .BR sem_post () | |
| 61 | is async-signal-safe: | |
| 62 | it may be safely called within a signal handler. | |
| 63 | .SH "SEE ALSO" | |
| 64 | .BR sem_getvalue (3), | |
| 65 | .BR sem_wait (3), | |
| 66 | .BR sem_overview (7) |