projects / thirdparty / man-pages.git / blame
| Commit | Line | Data |
|---|---|---|
| a1eaacb1 | 1 | '\" t |
| c11b1abf | 2 | .\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com> |
| 2c731798 | 3 | .\" |
| 5fbde956 | 4 | .\" SPDX-License-Identifier: Linux-man-pages-copyleft |
| 2c731798 | 5 | .\" |
| 4c1c5274 | 6 | .TH sem_post 3 (date) "Linux man-pages (unreleased)" |
| 2c731798 MK |
7 | .SH NAME |
| 8 | sem_post \- unlock a semaphore | |
| 87b2352b AC |
9 | .SH LIBRARY |
| 10 | POSIX threads library | |
| 8fc3b2cf | 11 | .RI ( libpthread ", " \-lpthread ) |
| 2c731798 MK |
12 | .SH SYNOPSIS |
| 13 | .nf | |
| 14 | .B #include <semaphore.h> | |
| 68e4db0a | 15 | .PP |
| 2c731798 MK |
16 | .BI "int sem_post(sem_t *" sem ); |
| 17 | .fi | |
| 18 | .SH DESCRIPTION | |
| 19 | .BR sem_post () | |
| 20 | increments (unlocks) the semaphore pointed to by | |
| 21 | .IR sem . | |
| 22 | If the semaphore's value consequently becomes greater than zero, | |
| c13182ef | 23 | then another process or thread blocked in a |
| 2c731798 MK |
24 | .BR sem_wait (3) |
| 25 | call will be woken up and proceed to lock the semaphore. | |
| 26 | .SH RETURN VALUE | |
| 27 | .BR sem_post () | |
| c13182ef | 28 | returns 0 on success; |
| 2c731798 MK |
29 | on error, the value of the semaphore is left unchanged, |
| 30 | \-1 is returned, and | |
| c13182ef | 31 | .I errno |
| 2c731798 MK |
32 | is set to indicate the error. |
| 33 | .SH ERRORS | |
| 34 | .TP | |
| 35 | .B EINVAL | |
| 36 | .I sem | |
| 37 | is not a valid semaphore. | |
| 642ff1cc MK |
38 | .TP |
| 39 | .B EOVERFLOW | |
| 40 | .\" Added in POSIX.1-2008 TC1 (Austin Interpretation 213) | |
| 41 | The maximum allowable value for a semaphore would be exceeded. | |
| c27b616f | 42 | .SH ATTRIBUTES |
| 8033b62c PH |
43 | For an explanation of the terms used in this section, see |
| 44 | .BR attributes (7). | |
| 45 | .TS | |
| 46 | allbox; | |
| c466875e | 47 | lbx lb lb |
| 8033b62c PH |
48 | l l l. |
| 49 | Interface Attribute Value | |
| 50 | T{ | |
| 9e54434e BR |
51 | .na |
| 52 | .nh | |
| c27b616f | 53 | .BR sem_post () |
| 8033b62c PH |
54 | T} Thread safety MT-Safe |
| 55 | .TE | |
| c466875e | 56 | .sp 1 |
| 3113c7f3 | 57 | .SH STANDARDS |
| 4131356c AC |
58 | POSIX.1-2008. |
| 59 | .SH HISTORY | |
| 2c731798 MK |
60 | POSIX.1-2001. |
| 61 | .SH NOTES | |
| 62 | .BR sem_post () | |
| 63 | is async-signal-safe: | |
| 64 | it may be safely called within a signal handler. | |
| a14af333 | 65 | .SH EXAMPLES |
| 40bc92e5 | 66 | See |
| 3d5a6df0 MK |
67 | .BR sem_wait (3) |
| 68 | and | |
| 69 | .BR shm_open (3). | |
| 47297adb | 70 | .SH SEE ALSO |
| 2c731798 MK |
71 | .BR sem_getvalue (3), |
| 72 | .BR sem_wait (3), | |
| 46fc35d5 | 73 | .BR sem_overview (7), |
| 28a4c58c | 74 | .BR signal\-safety (7) |