sh: 1: pause: not found

Welcome to the library management system, please type your commands.
> 1 added to the system.
> Fail! The book has not been borrowed.
> 2 added to the system.
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Welcome to the library management system, please type your commands.
> 1 added to the system.
> Fail! The book has not been borrowed.
> 2 added to the system.
> 3 added to the system.
> 4 added to the system.
> 5 added to the system.
> 6 added to the system.
> 7 added to the system.
> 8 added to the system.
> 9 added to the system.
> 10 added to the system.
> 11 added to the system.
> 12 added to the system.
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> 24 added to the system.
> 25 added to the system.
> 26 added to the system.
> 27 added to the system.
> 28 added to the system.
> 29 added to the system.
> 30 added to the system.
> 31 added to the system.
> 32 added to the system.
> 33 added to the system.
> 34 added to the system.
> 35