Learn Linux Shell Scripting - Fundamentals of Bash 4.4

Here strings

The last thing we'd like to discuss in this chapter is the here string. It is very similar to the here document (hence the name), but it deals with a single string, instead of a document (who would have thought!).

This construct, which uses the <<< syntax, can be used to supply text input to a command that perhaps normally only accepts input from stdin or a file. A good example for this is bc, which is a simple calculator (part of the GNU Project).

Normally, you use it in one of two ways: sending input to stdin via a pipe, or by pointing bc to a file:

reader@ubuntu:/tmp$ echo "2^8" | bc256reader@ubuntu:/tmp$ echo "4*4" > mathreader@ubuntu:/tmp$ bc mathbc 1.07.1Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006, 2008, 2012-2017 ...