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60 lines
2.5 KiB
Markdown
60 lines
2.5 KiB
Markdown
5 years ago
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# shell Programming
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* [Tutorial](https://www.tutorialspoint.com/unix/shell_scripting.htm)
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```sh
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#!/bin/sh
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echo "File Name: $0"
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echo "First Parameter : $1"
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echo "Second Parameter : $2"
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echo "Quoted Values: $@"
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echo "Quoted Values: $*"
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echo "Total Number of Parameters : $#"
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```
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* while loop
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```sh
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#!/bin/sh
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a=0
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while [ "$a" -lt 10 ] # this is loop1
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do
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b="$a"
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while [ "$b" -ge 0 ] # this is loop2
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do
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echo -n "$b "
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b=`expr $b - 1`
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done
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echo
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a=`expr $a + 1`
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done
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```
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* Assume variable **a** holds 10 and variable **b** holds 20 then
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| Operator | Description | Example |
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| :------: | :----------------------------------------------------------: | :------------------------: |
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| **-eq** | Checks if the value of two operands are equal or not; if yes, then the condition becomes true. | [ $a -eq $b ] is not true. |
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| **-ne** | Checks if the value of two operands are equal or not; if values are not equal, then the condition becomes true. | [ $a -ne $b ] is true. |
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| **-gt** | Checks if the value of left operand is greater than the value of right operand; if yes, then the condition becomes true. | [ $a -gt $b ] is not true. |
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| **-lt** | Checks if the value of left operand is less than the value of right operand; if yes, then the condition becomes true. | [ $a -lt $b ] is true. |
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| **-ge** | Checks if the value of left operand is greater than or equal to the value of right operand; if yes, then the condition becomes true. | [ $a -ge $b ] is not true. |
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| **-le** | Checks if the value of left operand is less than or equal to the value of right operand; if yes, then the condition becomes true. | [ $a -le $b ] is true. |
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| Operator | Description | Example |
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| :------: | :----------------------------------------------------------: | :-----------------------------------: |
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| **!** | This is logical negation. This inverts a true condition into false and vice versa. | [ ! false ] is true. |
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| **-o** | This is logical **OR**. If one of the operands is true, then the condition becomes true. | [ $a -lt 20 -o $b -gt 100 ] is true. |
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| **-a** | This is logical **AND**. If both the operands are true, then the condition becomes true otherwise false. | [ $a -lt 20 -a $b -gt 100 ] is false. |
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* Other [Operator](https://www.tutorialspoint.com/unix/unix-basic-operators.htm)
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