The if...then control structure has the following syntax (see page 398 for tcsh):
if test-command then commandsfi
The bold words in the syntax description are the items you supply to cause the structure to have the desired effect. The nonbold words are the keywords the shell uses to identify the control structure.
Figure 10-1 shows that the if statement tests the status returned by the test-command and transfers control based on this status. The end of the if structure is marked by a fi statement (if spelled backward). The following script prompts for two words, reads them, and then uses an if structure to execute commands based on the result returned by the test builtin (tcsh uses the test utility) ...