Validating user input in shell script

There are many parties involved in the building and deployment of a software product (even if there's only one developer), and the entities that interact with the resulting system are even more, and often with diverse interests.Among these entities there necessarily exists a complicated network of explicit and implicit trust relationships, which in all but the simplest situations is too difficult (often impossible) to analyze. /bin/bash ################################### ### Warning: Portability issue. ### ################################### _JAIL="

There are many parties involved in the building and deployment of a software product (even if there's only one developer), and the entities that interact with the resulting system are even more, and often with diverse interests.Among these entities there necessarily exists a complicated network of explicit and implicit trust relationships, which in all but the simplest situations is too difficult (often impossible) to analyze. /bin/bash ################################### ### Warning: Portability issue. ### ################################### _JAIL="$1" ## note double bracket syntax: if -z "$_JAIL" then echo "Please set \$_JAIL"else echo "Setting up jail at $_JAIL" //call setjail() // setjail fi#!

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After the mammoth previous section this one is much easier to get through.If we would like to ask the user for input then we use a command called read.This command takes the input and will save it into a variable.In computer security, there are often known good data — data the developer is completely certain is safe.There are also known bad characters; data the developer is certain is unsafe (can cause Code injection etc.).Input and output handling is to ensure that data passed between computing systems do not yield unexpected behaviour on the systems, i.e. There a few methods which can make data safe for handling, with different level of security and applicability: Validating data is to ensure that data is safe prior to use.

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