echo writes its arguments, separated by BLANKs and terminated by a NEWLINE, to the standard output.
echo is useful for producing diagnostics in command files and for sending known data into a pipe, and for displaying the contents of environment variables.
For example, you can use echo to determine how many subdirectories below the root directory (/) is your current directory, as follows:
echo your current-working-directory's full pathname
pipe the output through tr to translate the path's embedded slash-characters into space-characters
pipe that output through wc -w for a count of the names in your path.
example% /usr/bin/echo "echo $PWD | tr '/' ' ' | wc -w"
The shells csh(1), ksh(1), and sh(1), each have an echo built-in command, which, by default, will have precedence, and will be invoked if the user calls echo without a full pathname. /usr/ucb/echo and csh's echo() have an -n option, but do not understand back-slashed escape characters. sh's echo(), ksh's echo(), and /usr/bin/echo, on the other hand, understand the black-slashed escape characters, and ksh's echo() also understands \a as the audible bell character; however, these commands do not have an -n option.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
The -n option is a transition aid for BSD applications, and may not be supported in future releases.