sbt includes a process library to simplify working with external
processes. The library is available without import in build definitions
and at the interpreter started by the consoleProject
task.
To run an external command, follow it with an exclamation mark !:
"find project -name *.jar" !
An implicit converts the String to sbt.ProcessBuilder, which defines
the ! method. This method runs the constructed command, waits until
the command completes, and returns the exit code. Alternatively, the
run method defined on ProcessBuilder runs the command and returns an
instance of sbt.Process, which can be used to destroy the process
before it completes. With no arguments, the ! method sends output to
standard output and standard error. You can pass a Logger to the !
method to send output to the Logger:
"find project -name *.jar" ! log
Two alternative implicit conversions are from scala.xml.Elem or
List[String] to sbt.ProcessBuilder. These are useful for
constructing commands. An example of the first variant from the android
plugin:
<x> {dxPath.absolutePath} --dex --output={classesDexPath.absolutePath} {classesMinJarPath.absolutePath}</x> !
If you need to set the working directory or modify the environment, call
sbt.Process explicitly, passing the command sequence (command and
argument list) or command string first and the working directory second.
Any environment variables can be passed as a vararg list of key/value
String pairs.
Process("ls" :: "-l" :: Nil, Path.userHome, "key1" -> value1, "key2" -> value2) ! log
Operators are defined to combine commands. These operators start with
# in order to keep the precedence the same and to separate them from
the operators defined elsewhere in sbt for filters. In the following
operator definitions, a and b are subcommands.
a #&& b Execute a. If the exit code is nonzero, return that exit
code and do not execute b. If the exit code is zero, execute b and
return its exit code.
a #|| b Execute a. If the exit code is zero, return zero for the
exit code and do not execute b. If the exit code is nonzero, execute
b and return its exit code.
a #| b Execute a and b, piping the output of a to the input
of b.
There are also operators defined for redirecting output to Files and
input from Files and URLs. In the following definitions, url is an
instance of URL and file is an instance of File.
a #< url or url #> a Use url as the input to a. a may be a
File or a command.
a #< file or file #> a Use file as the input to a. a may be
a File or a command.
a #> file or file #< a Write the output of a to file. a may
be a File, URL, or a command.
a #>> file or file #<< a Append the output of a to file. a may
be a File, URL, or a command.
There are some additional methods to get the output from a forked
process into a String or the output lines as a Stream[String]. Here
are some examples, but see the
ProcessBuilder API for details.
val listed: String = "ls" !!
val lines2: Stream[String] = "ls" lines_!
Finally, there is a cat method to send the contents of Files and
URLs to standard output.
Download a URL to a File:
url("http://databinder.net/dispatch/About") #> file("About.html") !
// or
file("About.html") #< url("http://databinder.net/dispatch/About") !
Copy a File:
file("About.html") #> file("About_copy.html") !
// or
file("About_copy.html") #< file("About.html") !
Append the contents of a URL to a File after filtering through
grep:
url("http://databinder.net/dispatch/About") #> "grep JSON" #>> file("About_JSON") !
// or
file("About_JSON") #<< ( "grep JSON" #< url("http://databinder.net/dispatch/About") ) !
Search for uses of null in the source directory:
"find src -name *.scala -exec grep null {} ;" #| "xargs test -z" #&& "echo null-free" #|| "echo null detected" !
Use cat:
val spde = url("http://technically.us/spde/About")
val dispatch = url("http://databinder.net/dispatch/About")
val build = file("project/build.properties")
cat(spde, dispatch, build) #| "grep -i scala" !
