e is ${#varname}, which returns the length of the value of the variable as a character string. For example, if filename has the value fred.c, then ${#filename} would have the value 6.... d}
If varname exists and isn't null, return its value; otherwise set it to word and then return its value.[7]
Purpose:
Setting a variable to a default ... N, if it exists, with no arguments; if its return value is non-zero: exits the script with the same code. The default value is main.
Exits the script with the return code o... lse, the test failed. Remembering that the return value of a function is the return value of its last executed command, the functions dotes
operations and comparisons on variables
#+ whose value consists of all-integer characters.
# Caution ad... tring has not been initialized, it has no defined value.
# This state is called "null" (not the same as z
