Shell Programming Learning: branching structure and looping structure

One. If structure

1. Single branch structure

If condition
then
    statement1
    statement2
    ...
Fi

2. Dual-Branch structure

If condition
then
    statement1
    statement2
    ...
else
    statement3
    statement4
fi

3. Multi-branch structure

If condition
then 
    statement
elif    condition2 then statement2
fi

Second: Case structure

Case condition in
pattern1)
    statment
    ;;
PATTERN2)
    statement2
    ;;
....
Esac

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Three: The while statement of the loop structure

1. When-type loop structure (while)

While condition
do
    statement1
    statement2
... Done

Executes when condition is true

2. Until the type cycle structure (until)

Until condition
do
    statement1
    statement2
Done

When the condition to meet the end

Base provides two circular control statements, break: Used to jump out of loop control, continue: Just end this loop, and start the next round of loops.

3.foreach Loops and Counting loops

For variable in wordlist
do
    statement1
    statement2
    ...
Done

In the structure in wordlist can be omitted, omitted after the equivalent in "$@"

4: For loop structure in C language

For ((EXP1;EXP2;EXP3))
do
    statment1
    statment2
... Done