Loops

For loop

for <varname>; do
    commands;
done

• Iterates through a loop once for each command-line argument.
• Stores the value of the current argument in the specified variable.

for arg; do
    echo "Argument: $arg"
done

For-in loop

for <varname> in <list of values>; do
    commands;
done

• Iterates through a loop once for each value in the specified list.
• Stores the value of the current list item in the specified variable.

for item in apple orange; do
   echo "List item: $item"
done

for value in $@; do
   echo "List item: $value"
done

for img in *.png; do echo $img; done

for img in *.png; do
    echo $img;
done

While loop

while <command>; do
    commands;
done

• Iterates through a loop as long as the specified command is true.

index="3"
while [ "$index" -gt "0" ]; do
    echo Index: $index
    let index=index-1
done

Until loop

until <command>; do
    commands;
done

• Iterates through a loop as long as the specified command is not true.

index="3"
until [ "$index" -eq "0" ]; do
    echo "Index: $index"
    let "index = index - 1"
done

Jump statements

• break [n]  : Break from the innermost n loops (the default is 1).
• continue [n]  : Continue on to the next iteration of the innermost n loops (the default is 1).