Re: [Help-bash] pipe character at end of command ?

[Greg Wooledge]

On Wed, Nov 23, 2016 at 03:46:17PM +0000, Ulf Andersson A wrote:
> spunk()
> {
>    sed '/Ape/d'    |
>    sed '/Banana/d' |
>    sed '/Ladder/d'
> }
> 
> cat $0 | spunk
> --8><--------------------------------------------
> I have figured out what the three sed commands do each by themselves, but I 
> have still fo figure out what the pipe characters actually do here. And no, I 
> did not forget to put any continuation characters at the end of the lines.

The function is exactly equivalent to this:

spunk() {
  sed '/Ape/d' | sed '/Banana/d' | sed '/Ladder/d'
}

When you write a line in such a way that there *must be more* of it in
order to make a complete command, bash continues reading the next
line to get the rest of the command.  In these cases, an explicit \ is
not needed.

Try it interactively, with simple cases, and you'll see:

imadev:~$ echo true |
> cat 
true

imadev:~$ true &&
> echo yes
yes

imadev:~$ echo "hello
> world"
hello
world

"> " is bash's default value for PS2, the internal variable that's used
to prompt for the continuation of a multi-line command.

When writing long commands in a script, most people will try to divide
up the command in a way that makes it easy to read (for humans).  When
there are natural divisions like |, it makes sense to use these.

The following two multi-line commands are completely equivalent, but
one of them is much easier to read than the other:

sed '/Ape/d'    |
sed '/Banana/d' |
sed '/Ladder/d'

sed '/Ape/d' | sed \
'/Banana/d' | sed '/Ladder/d'