How do I get a number in shell?

How do I get a number in shell? -- Linux general technology-Linux programming and kernel information. The following is a detailed description. [I = s] This post was last edited by Growth MB

For example:

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How to extract and add the numbers above

The result of grep-o '[0-9]' is as follows:
1
2
3
4
5
6
...........

The result is as follows:
123
456
123
456

And then add them together?

The preceding number is not fixed with three digits. it may have only one digit or four digits .. Is the data that is dynamically read...

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