1, in the format:
What if? Statement format
What if? situation
then
order
other
order
Fi, don't forget three conditional expressions ending in 2, if:
What if? Command? then
What if? Function? The then command is executed successfully, which is equal to returning 0? (such as grep? , find a match)? Failed to execute, returned non-0? (grep, no match found)
What if? [? expression_r_r_r？ ]? If the result of then expression is true, it returns 0, and if leads the value of 0 to then.
What if? Testing? expression_r_r_r？ If the result of the then expression is false, a non-zero value is returned, and if leads the non-zero value to then.