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Loops

For-loop

Two ways are available to perform a for-loop:

#!/bin/bash
 
echo "1st method"
for ((i=0; i<5; i=i+1)); do
    echo $i
done
 
echo "2nd method"
for i in {4..0}; do
    echo $i
done

#!/bin/bash
 
i=0
while [[ i -lt 5 ]]; do
    echo $i
    i=$((i + 1))
done

expression	is TRUE if
`<str>`	`<str>` is not null
`-n <str>`	`<str>` length is greater than zero
`-z <str>`	`<str>` length is zero
`<str1> == <str2>`	`<str1>` and `<str2>` are equal
`<str1> != <str2>`	`<str1>` and `<str2>` are not equal
`<str1> > <str2>`	`<str1>` comes after `<str2>` in lexicographically order
`<str1> < <str2>`	`<str1>` comes before `<str2>` in lexicographically order

expression	is TRUE if
`<int1> -eq <int2>`	`<int1>` is equal to `<int2>`
`<int1> -ne <int2>`	`<int1>` is not equal to `<int2>`
`<int1> -le <int2>`	`<int1>` is less than or equal to `<int2>`
`<int1> -lt <int2>`	`<int1>` is less than `<int2>`
`<int1> -ge <int2>`	`<int1>` is greater than or equal to `<int2>`
`<int1> -gt <int2>`	`<int1>` is greater than `<int2>`