Shell programming constructs

The shell programming language has several constructs that give added flexibility to your programs:

• Comments let you document the function of a program.

• The here document allows you to include, within the shell program itself, lines to be redirected as input to some command in the shell program.

• The exit command lets you terminate a program at a point other than the end of the program and use return codes.

• The looping constructs, for and while, allow a program to iterate through groups of commands in a loop.

• The conditional control commands, if and case, execute a group of commands only if a particular set of conditions is met.

• The break command allows a program to exit unconditionally from a loop.