flow control

summary

This subchapter looks at flow control in UNIX (and Linux).

flow control

This subchapter looks at flow control in UNIX (and Linux).

The three basic kinds of instructions in structured programming are: sequence, decision, and loop.

A sequence is a series of instructions performed in the same order every time.

A decision makes a choice between two or more different possible sequences of instructions.

A loop repeats a sequence of instructions repeatedly.

The basic two flow control decision statements are if and case.

The basic three flow control loops are while, for, and select.

if

The basic format of the if statement:

if list1 ; then list2 ; elif list3 ; then list4 else list5 fi

case

The basic format of the case statement:

case expression in
pattern1) list1 ;;
…
patternN) listN ;;
esac

while

The basic format of the while loop:

while expression ; do list ; done

for

The basic format of the for loop:

for var in word1 … wordN ; do list ; done

select

The basic format of the select loop:

select var in word1 … wordN ; do list ; done