if command

Synopsis

if <test statement>
then
    <statements>
fi

if <test statement>
then
    <statements>
else
    <statements>
fi

Description

The if command is used to conditionally execute statements.

test statement

Any command. The test statement set the $? variable. If the value of $? becomes 0 (true) the statements after the then statement will be executed. Otherwise the statements after the else statement.

Examples

The examples shows how the value of a numeric variable can be tested with the itest command.

=> a=1; if itest $a == 0; then echo true; else echo false; fi
false
=> a=0; if itest $a == 0; then echo true; else echo false; fi
true

In the following example we try to load an EFI binary via TFTP. If loading succeeds, the binary is executed.

if tftp $kernel_addr_r shellriscv64.efi; then bootefi $kernel_addr_r; fi

Return value

The value of $? is the return value of the last executed statement.

=> if true; then true; else true; fi; echo $?
0
=> if false; then true; else true; fi; echo $?
0
=> if false; then false; else false; fi; echo $?
1
=> if true; then false; else false; fi; echo $?
1
=> if false; then true; fi; echo $?
1