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.. SPDX-License-Identifier: GPL-2.0-or-later
.. index::
single: if (command)
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.
Example
-------
The examples shows how the value of a numeric variable can be tested with
**itest**.
::
=> 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
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