OSTRICH is an SMT solver for string constraints.
For the POPL 2019 version, please use the popl2019 branch.
After installing the Scala Build tool (SBT), you can assemble a JAR file using sbt assembly. To run it, use either the ostrich script in the root folder, or ostrich-client. The latter transparently spins up a server that continuously serves requests from the client script; useful to avoid cold-starting the JVM if you are running many instances.
See ./ostrich -help for more options.