9.13 Multiline Commands, Secondary Prompts
Both the Bourne shell and the C shell support multiline commands.
In the Bourne shell, a newline following an open quote (
In the C shell, you can continue a line by
typing a backslash (
Obviously, this is a convenience if you're typing a long command line. It is a minor feature and one easily overlooked; however, it makes it much easier to use a program like sed ( 34.24 ) from the command line. For example, if you know you chronically make the typos "mvoe" (for "move") and "thier" (for "their"), you might be inspired to type the following command:
More importantly, the ability to issue multiline
commands lets you use the shell's programming
features interactively from the command line.
In both the Bourne and the C shell, multiline programming constructs
automatically generate a secondary prompt (
For example, here's a place to use my favorite programming construct for non-programmers, the for loop ( 9.12 ) :
Or in the C shell with foreach ( 9.11 ) :
While a simple command like this could be saved into a shell script ( 1.5 ) , it is often even easier to use it interactively.
Users of sed should of course makesure their script works correctly before overwritingtheir original file . ( 34.3 )