piping-into-commands.md

Piping into Commands

The CommandBox interactive shell already allows for a command to pipe data into another Command.

cat myfile.txt | grep "find me"

Since CommandBox commands don't have a "standard input", the output of the previous command is passed into the second command as its first parameter. In this instance, the grep command's first parameter is called input so it receives the value returned by the cat command. The "find me" text becomes the second parameter-- in this case, expression.

Examples

There is nothing special about a parameter that can received piped input. In fact, any command can receive piped input for its first parameter. The following commands all accomplish the same thing.

coldbox create app "My App"

echo "My App" | coldbox create app

echo "My App" > appName.txt
cat appName.txt | coldbox create app

This allows you to get creative by combining commands together like so:

package set name="hello world"
package show name | sed s/hello/goodbye/

This takes a package name and replaces some text on output. One benefit is that Windows users don't have a native sed command in their OS, but those commands inside a CommandBox Recipe will execute consistently on any machine.

Piping From The OS

What if you aren't using the interactive shell and you want to pipe into CommandBox from your OS's native shell? This is also supported, and as long as there is a command specified, the piped input will become the first parameter as before.

C:\> echo coldbox | box install
C:\> echo reverse('this is a test') | box repl

If you pipe text directly into the box executable with no command specified in the parameters, each line of your piped text will be read from the standard input as a command.

C:\> echo version | box
C:\> box < commands.txt