Shell script: If-else

The Shell has three kinds of if ... else statements:

1.if. FI statement;

2.if ... else ... fi statement;

3.if. Elif ... else .... fi statement.

If ... fi statement

Syntax for the IF ... else statement:

if [Expression]  Then If Truefi     

Note: There must be a space between expression and square brackets ([]), or there will be a syntax error.

If ... else ... fi statement

Syntax for the If ... else ... fi statement

if [Expression]  Then  If Trueelse If True fi       

If ... elif ... else ... fi statement

Syntax for the If ... else ... elif. Fi statement

if[Expression1 ] ThenStatement (s) to be executedifExpression1Istrueelif[Expression2 ] ThenStatement (s) to be executedifExpression2Istrueelif[Expression3 ] ThenStatement (s) to be executedifExpression3IstrueElseStatement (s) to be executedifNo expression istruefi

If-else statement that mates with test

The IF ... Else statement is also often used in conjunction with the Test command, as follows:

num1=1num2=2if test ${num1}-eq ${num2}then    Echo  'thenumbers is equal! ' Else    Echo ' The numbers is not equal! ' fi

Shell script: If-else