How to get shell expansion on scala sys.process invocations - scala

Question

Consider a simple attempt at shell expansion:
Simple/direct approach :
scala> ("/bin/ls /tmp/*" run BasicIO(false, sb, None)).exitValue
ls: /tmp/*: No such file or directory
res18: Int = 1
I have tried a number of combinations of ProcessIO, BasicIO, Process, etc and can not figure out how to get shell expansion to work.
bash -c :
scala> ("bash -c \"/bin/ls /tmp/*\"" run BasicIO(false, sb, None)).exitValue
/tmp/*": -c: line 0: unexpected EOF while looking for matching `"'
/tmp/*": -c: line 1: syntax error: unexpected end of file
res19: Int = 2
Pipe to bash -s :
scala> ("echo \"/bin/ls /tmp/*\" | bash -s") run BasicIO(false, sb, None)).exitValue
<console>:1: error: ';' expected but ')' found.
("echo \"/bin/ls /tmp/*\" | bash -s") run BasicIO(false, sb, None)).exitValue
btw that last one in shell looks like the following (and works):
21:28:32/dstat $echo "/bin/ls /tmp/*" | bash -s
/tmp/OSL_PIPE_501_SingleOfficeIPC_a974a3af70d46eaeed927022833718b7
/tmp/oobelib.log
/tmp/spark-steve-org.apache.spark.deploy.master.Master-1.pid
/tmp/spark-steve-org.apache.spark.deploy.worker.Worker-1.pid
/tmp/KSOutOfProcessFetcher.501.qQkpPp2uZLdVc5pukHmfJMR4bkM=:
Shell escaping would also be of interest to understand wrt scala Process classes: an example including both expansion and escaping would be optimal.
UPDATE I found this JIRA - it may be relevant. I hope not - that means there were little/no hope for the functionality described here..
sys.process._ is so restrictive in what it can accept that is not usable https://issues.scala-lang.org/browse/SI-7027
Another update I found an old email thread involving the esteemed Daniel Sobral who mentions:
Because the quotes are not delimiting the parameter passed to bash --
it is Scala who decides how the arguments break up, and it simply
splits on spaces, without any quotation facility. If you try the
following, instead, it will work:
Seq("bash", "-c", "ls *.scala").!
It is looking ever more grim for a "fire and forget" version of running a shell command. I yearn for the ruby
%x{whatever shell string you want goes here}
e.g.
echo 'print %x{ls -lrtad /etc/* 2>&1}' | ruby
Which most satisfyingly returns:
-r--r--r-- 1 root wheel 69836 May 28 2013 /etc/php.ini.default-
5.2-previous~orig
lrwxr-xr-x 1 root wheel 30 Oct 22 2013 /etc/localtime -> /usr/share/zoneinfo/US/Pacific
-rw-r--r-- 1 root wheel 102 Nov 5 2013 /etc/hostconfig
-rw-r--r-- 1 root wheel 1286 Nov 5 2013 /etc/my.cnf
-rw-r--r-- 1 root wheel 4161 Dec 18 2013 /etc/sshd_config~previous
-rw-r--r-- 1 root wheel 199 Feb 7 2014 /etc/shells
-rw-r--r-- 1 root wheel 0 Sep 9 2014 /etc/xtab
-rw-r--r-- 1 root wheel 1316 Sep 9 2014 /etc/ttys
.. etc
but looks like that were not happening with Scala..

Answer 1

I fear you took my answer the wrong way. Ruby is doing the same thing, and I know this without looking at their code because what Java (and, by extension, Scala) presents as API is a direct translation of the Unix API.
It is shell that does shell expansions, and while it's perfectly possible for any other software to emulate them, it would be a losing game. Wildcards are often provided, but they are a small part of shell expansion.
My answer has everything you need, but let me expand on that:
import scala.sys.process._
implicit class RubyX(val sc: StringContext) extends AnyVal {
def x(args: Any*): ProcessBuilder = {
val strings = sc.parts.iterator
val expressions = args.iterator
var buf = new StringBuffer(strings.next)
while(strings.hasNext) {
buf append expressions.next
buf append strings.next
}
Process(Seq("bash", "-c", buf.toString))
}
}
then you can do
x"ls *.scala".!
I returned a ProcessBuilder, so you can pick whatever is the best form of execution for you, such as ! above that returns the exit code and echoes everything else to stdout.