projects / thirdparty / man-pages.git / blame
| Commit | Line | Data |
|---|---|---|
| c11b1abf | 1 | .\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com> |
| 2c731798 | 2 | .\" |
| 5fbde956 | 3 | .\" SPDX-License-Identifier: Linux-man-pages-copyleft |
| 2c731798 | 4 | .\" |
| 7bd6328f | 5 | .TH SEM_POST 3 2021-03-22 "Linux man-pages (unreleased)" "Linux Programmer's Manual" |
| 2c731798 MK |
6 | .SH NAME |
| 7 | sem_post \- unlock a semaphore | |
| 87b2352b AC |
8 | .SH LIBRARY |
| 9 | POSIX threads library | |
| 8fc3b2cf | 10 | .RI ( libpthread ", " \-lpthread ) |
| 2c731798 MK |
11 | .SH SYNOPSIS |
| 12 | .nf | |
| 13 | .B #include <semaphore.h> | |
| 68e4db0a | 14 | .PP |
| 2c731798 MK |
15 | .BI "int sem_post(sem_t *" sem ); |
| 16 | .fi | |
| 17 | .SH DESCRIPTION | |
| 18 | .BR sem_post () | |
| 19 | increments (unlocks) the semaphore pointed to by | |
| 20 | .IR sem . | |
| 21 | If the semaphore's value consequently becomes greater than zero, | |
| c13182ef | 22 | then another process or thread blocked in a |
| 2c731798 MK |
23 | .BR sem_wait (3) |
| 24 | call will be woken up and proceed to lock the semaphore. | |
| 25 | .SH RETURN VALUE | |
| 26 | .BR sem_post () | |
| c13182ef | 27 | returns 0 on success; |
| 2c731798 MK |
28 | on error, the value of the semaphore is left unchanged, |
| 29 | \-1 is returned, and | |
| c13182ef | 30 | .I errno |
| 2c731798 MK |
31 | is set to indicate the error. |
| 32 | .SH ERRORS | |
| 33 | .TP | |
| 34 | .B EINVAL | |
| 35 | .I sem | |
| 36 | is not a valid semaphore. | |
| 642ff1cc MK |
37 | .TP |
| 38 | .B EOVERFLOW | |
| 39 | .\" Added in POSIX.1-2008 TC1 (Austin Interpretation 213) | |
| 40 | The maximum allowable value for a semaphore would be exceeded. | |
| c27b616f | 41 | .SH ATTRIBUTES |
| 8033b62c PH |
42 | For an explanation of the terms used in this section, see |
| 43 | .BR attributes (7). | |
| c466875e MK |
44 | .ad l |
| 45 | .nh | |
| 8033b62c PH |
46 | .TS |
| 47 | allbox; | |
| c466875e | 48 | lbx lb lb |
| 8033b62c PH |
49 | l l l. |
| 50 | Interface Attribute Value | |
| 51 | T{ | |
| c27b616f | 52 | .BR sem_post () |
| 8033b62c PH |
53 | T} Thread safety MT-Safe |
| 54 | .TE | |
| c466875e MK |
55 | .hy |
| 56 | .ad | |
| 57 | .sp 1 | |
| 3113c7f3 | 58 | .SH STANDARDS |
| 2c731798 MK |
59 | POSIX.1-2001. |
| 60 | .SH NOTES | |
| 61 | .BR sem_post () | |
| 62 | is async-signal-safe: | |
| 63 | it may be safely called within a signal handler. | |
| a14af333 | 64 | .SH EXAMPLES |
| 40bc92e5 | 65 | See |
| 3d5a6df0 MK |
66 | .BR sem_wait (3) |
| 67 | and | |
| 68 | .BR shm_open (3). | |
| 47297adb | 69 | .SH SEE ALSO |
| 2c731798 MK |
70 | .BR sem_getvalue (3), |
| 71 | .BR sem_wait (3), | |
| 46fc35d5 | 72 | .BR sem_overview (7), |
| 28a4c58c | 73 | .BR signal\-safety (7) |