Execing Processes in Clojure

Our example demonstrates how to replace the current process with another one using Clojure. This is similar to the classic exec function in Unix-like operating systems.

(ns execing-processes
  (:require [clojure.java.shell :as shell]))

(defn exec-ls []
  (let [binary "ls"
        args ["-a" "-l" "-h"]]
    (try
      (let [result (apply shell/sh (cons binary args))]
        (println (:out result)))
      (catch Exception e
        (println "Error executing command:" (.getMessage e))))))

(defn -main []
  (exec-ls))

For our example, we’ll execute the ls command. Clojure doesn’t have a direct equivalent to Go’s exec.LookPath, so we assume ls is in the system’s PATH.

We define the arguments for ls in a vector. In this case, we’re using the -a, -l, and -h options.

Clojure doesn’t have a direct equivalent to syscall.Exec. Instead, we use the clojure.java.shell/sh function to execute external commands. This function doesn’t replace the current process but runs the command as a subprocess and captures its output.

When we run our program, it will execute ls and print its output:

$ lein run
total 8
drwxr-xr-x  4 user  group   128B Apr 15 10:00 .
drwxr-xr-x  8 user  group   256B Apr 15 09:55 ..
-rw-r--r--  1 user  group   420B Apr 15 10:00 execing_processes.clj
-rw-r--r--  1 user  group   175B Apr 15 09:58 project.clj

Note that Clojure, being a JVM language, doesn’t offer a classic Unix fork function or a way to completely replace the current process. However, the ability to execute external processes covers many use cases where you might use exec in other languages.

To run this Clojure program, you would typically use a build tool like Leiningen. Create a project.clj file in the same directory as your Clojure file:

(defproject execing-processes "0.1.0-SNAPSHOT"
  :description "Execing Processes Example"
  :dependencies [[org.clojure/clojure "1.10.1"]]
  :main execing-processes)

Then you can run the program using:

$ lein run

This will compile your Clojure code and execute the -main function.