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update shell

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JMARyA 2024-03-07 08:33:09 +01:00
parent 50ed173d7d
commit a9a5c022bd
Signed by: jmarya
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11
technology/applications/cli/Shell.md
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@ -51,7 +51,7 @@ rm -v *.txt
``` ```
## Redirections ## Redirections
### 1. **Standard Input, Output, and Error** ### **Standard Input, Output, and Error**
In a shell environment, there are three standard streams: In a shell environment, there are three standard streams:
- **Standard Input (stdin - fd 0):** Represents the input to a command. - **Standard Input (stdin - fd 0):** Represents the input to a command.
- **Standard Output (stdout - fd 1):** Represents the output of a command. - **Standard Output (stdout - fd 1):** Represents the output of a command.
@ -182,6 +182,15 @@ ${fruits[*]}
${fruits[@]} ${fruits[@]}
``` ```
Use variable or `default` if the variable does not exist:
```shell
VR1=Value
MYVAR=${VR1:-default} # $MYVAR is 'Value'
#VR2=Value
MYVAR=${VR2:-default} # $MYVAR is 'default'
```
### Conditionals ### Conditionals
You can use conditional statements. You can use conditional statements.
```shell ```shell