if (1) - Linux Man Pages
if: conditionally execute a command
Synopsisif CONDITION; COMMANDS_TRUE...; [else; COMMANDS_FALSE...;] end
Descriptionif will execute the command CONDITION. If the condition's exit status is 0, the commands COMMANDS_TRUE will execute. If the exit status is not 0 and else is given, COMMANDS_FALSE will be executed.
In order to use the exit status of multiple commands as the condition of an if block, use begin; ...; end and the short circuit commands and and or.
if test -f foo.txt echo foo.txt exists else echo foo.txt does not exist end