Linux Advanced Bash Programming (Process Control If-else)

One: Condition judgment

if condition
Then
Statements
[elif condition
Then statements. ..]
[Else
Statements ]
fi

Integer comparison:

-lt, less than-le, less than or equal to-eq, equal to-ge, greater than or equal to-GT, greater than-ne, not equal to

Bash Script debug: Bash-x test.sh

Practice:

1: Write a bash program to determine the size of the parameters that are brought in.

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2: Prompt the user to enter a number, need to verify whether to enter a pure number? And judge whether it is odd or even!

Method 1: Use the arithmetic operation expr $n + 1 To determine whether it is a pure number, if it is not a pure number, then the command execution fails, thereby $? nonzero. ($? Indicates the result of the previous line of command 0 is successful, others are not successful)

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Method two: By using grep to determine whether the user's input contains non-numeric, if not included, then output 0, if included, Output 1.

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Validation results: The script names of the two methods are if2.sh,if3.sh

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Linux Advanced Bash Programming (Process Control If-else)