# sem
## Command Function
This command is used to query information about kernel semaphores.
## Syntax
sem \[_ID__ / fulldata_\]
## Parameters
**Table 1** Parameter description
Parameter
Parameters
Value Range
ID
Specifies the semaphore ID.
[0, 1023] or [0x0, 0x3FF]
fulldata
Queries information about all the semaphores in use. The information includes SemID, Count, OriginalCount, Creater(TaskEntry), and LastAccessTime.
N/A
## Usage
- If no parameter is specified, this command displays the semaphore IDs and the number of times that each semaphore is used.
- If **ID** is specified, the use of the specified semaphore is displayed.
- The **fulldata** parameter depends on **LOSCFG\_DEBUG\_SEMAPHORE**. Before using this parameter, select **Enable Semaphore Debugging** on **menuconfig**.
Debug ---\> Enable a Debug Version ---\> Enable Debug LiteOS Kernel Resource ---\> Enable Semaphore Debugging
## Example
- Run **sem**.
- Configure **LOSCFG\_DEBUG\_SEMAPHORE** and run **sem fulldata**.
## Output
Example 1: brief semaphore information
```
OHOS # sem
SemID Count
---------- -----
0x00000000 1
SemID Count
---------- -----
0x00000001 0
SemID Count
---------- -----
0x00000002 0
SemID Count
---------- -----
0x00000003 1
SemID Count
---------- -----
0x00000004 0
SemID Count
---------- -----
0x00000005 1
SemID Count
---------- -----
0x00000006 0
```
**Table 2** Output
Parameter
Description
SemID
Semaphore ID
Count
Number of times that the semaphore is used
> **NOTE:**
>The **ID** value can be in decimal or hexadecimal format.
>When **ID** is a value within \[0, 1023\], semaphore information of the specified ID is displayed. If the specified semaphore is not used, a message is displayed to inform you of this case. For other values, a message is displayed indicating that the parameter is incorrect.
Example 2: detailed semaphore information
```
OHOS # sem fulldata
Used Semaphore List:
SemID Count OriginalCount Creater(TaskEntry) LastAccessTime
------ ------ ------------- ------------------ --------------
0xb 0x0 0x0 0x404978fc 0xa1
0xc 0x0 0x0 0x404978fc 0xa1
0xd 0x0 0x0 0x404978fc 0x12c
0x10 0x0 0x0 0x404978fc 0x195
0xf 0x0 0x0 0x404978fc 0x195
0x11 0x0 0x0 0x4041a998 0x1d5
0x15 0x0 0x0 0x404978fc 0x273
0x14 0x0 0x0 0x404978fc 0x273
0x18 0x0 0x0 0x404978fc 0x352
0x17 0x0 0x0 0x404978fc 0x352
0x16 0x0 0x0 0x404978fc 0x352
0x1d 0x1 0x1 0x404978fc 0x385
0x1e 0x1 0x1 0x404978fc 0x388
0x1f 0x1 0x1 0x404978fc 0x38d
0x20 0x1 0x1 0x404978fc 0x38f
0x21 0x1 0x1 0x404978fc 0x392
0x3d 0x1 0x1 0x404978fc 0x395
0x3b 0x1 0x1 0x404978fc 0x395
0x3c 0x1 0x1 0x404978fc 0x395
0x39 0x1 0x1 0x404978fc 0x395
0x3a 0x1 0x1 0x404978fc 0x395
0x33 0x1 0x1 0x404978fc 0x395
0x35 0x1 0x1 0x404978fc 0x395
0x34 0x1 0x1 0x404978fc 0x395
0x38 0x1 0x1 0x404978fc 0x395
```
**Table 3** Output description
Parameter
Description
SemID
Semaphore ID
Count
Number of times that the semaphore is used
OriginalCount
Original count of the semaphore
Creater
Address of the entry function of the thread used to create the semaphore