sh

user=> (use '[clojure.java.shell :only [sh]])

;; Note: The actual output you see from a command like this will look messier.
;; The output below has had all newline characters replaced with line
;; breaks.  You would see a big long string with \n characters in the middle.
user=> (sh "ls" "-aul")

{:exit 0, 
 :out "total 64
drwxr-xr-x  11 zkim  staff    374 Jul  5 13:21 .
drwxr-xr-x  25 zkim  staff    850 Jul  5 13:02 ..
drwxr-xr-x  12 zkim  staff    408 Jul  5 13:02 .git
-rw-r--r--   1 zkim  staff     13 Jul  5 13:02 .gitignore
-rw-r--r--   1 zkim  staff  12638 Jul  5 13:02 LICENSE.html
-rw-r--r--   1 zkim  staff   4092 Jul  5 13:02 README.md
drwxr-xr-x   2 zkim  staff     68 Jul  5 13:15 classes
drwxr-xr-x   5 zkim  staff    170 Jul  5 13:15 lib
-rw-r--r--@  1 zkim  staff   3396 Jul  5 13:03 pom.xml
-rw-r--r--@  1 zkim  staff    367 Jul  5 13:15 project.clj
drwxr-xr-x   4 zkim  staff    136 Jul  5 13:15 src
", :err ""}

user=> (use '[clojure.java.shell :only [sh]])

user=> (println (:out (sh "cowsay" "Printing a command-line output")))

 _________________________________ 
< Printing a command-line output. >
 --------------------------------- 
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

nil

user=> (use '[clojure.java.shell :only [sh]])
nil

;; note that the options, like :in, have to go at the end of arglist
;; advantage of piping-in thru stdin is less need for quoting/escaping
user=> (println (:out (sh "cat" "-" :in "Printing input from stdin with funny chars like ' \" $@ & ")))
Printing input from stdin with funny chars like ' " $@ & 
nil

;; sh is implemented using Clojure futures.  See examples for 'future'
;; for discussion of an undesirable 1-minute wait that can occur before
;; your standalone Clojure program exits if you do not use shutdown-agents.

(sh "pwd" :dir "/home/ics/icsdev")
{:exit 0, :out "/home/ics/icsdev\n", :err ""}

(require '[clojure.java.shell :as shell])
(shell/sh "sh" "-c" "cd /etc; pwd")
{:exit 0, :out "/etc\n", :err ""}

;; note that you have to split you script by whitespace 
;; that was confusing for me 
;; for example script: 
;; "terraform plan -var param1=value1 -var param2=value2 -var-file=/etc/var.tfvars"

(shell/sh "terraform" "plan" "-var" "param=value" "-var" "param2=value2" "-var-file=/etc/var.tfvars")

;; feed the sh with environment variables
;; (note that $HELLO in our command line wouldn't work since we act as the shell here)

(require '[clojure.java.shell :as shell])
(shell/sh "printenv" "HELLO" :env {"HELLO" "Hello, World!"})
{:exit 0, :out "Hello, World!\n", :err ""}

;; override environment variables
;; BAD EXAMPLE since i guess lein uses a lot of env vars for coordination
;; but anyway

(require '[clojure.java.shell :as shell])

(sh/sh "lein" "compile")
{:exit 0,
 :out
 "WARNING: You have $CLASSPATH set, probably by accident.
  It is strongly recommended to unset this before proceeding.",
 :err ""}

;; note that
(sh/sh "lein" "compile" :env {})
;; will make lein quite confused.

;; we better modify the current env:

(let [current-env (into {} (System/getenv))]
  (sh/sh "lein" "compile" :env (dissoc current-env "CLASSPATH"))
{:exit 0, :out "", :err ""}


;; (into {} ...) is needed because System/getenv returns a map of type
;; java.util.Collections$UnmodifiableMap

;; on windows, the above examples won't work. try with an exe instead :)
(require '[clojure.java.shell :as shell])
(shell/sh "notepad.exe")
;; now notepad should be open!

;; On Windows, the Java shell needs to execute a program 
;; that executes the command: usually PowerShell, Bash, or cmd. 

;; So your `sh` function should invoke "powershell" OR "bash" and -c" 
;; OR "cmd and "/c" before your command. 

;; Instead of 
(clojure.java.shell/sh "ls")

;; you would do this

(clojure.java.shell/sh "powershell" "ls")

;; or this

(clojure.java.shell/sh "bash" "-c" "ls")

;; or this

(clojure.java.shell/sh "cmd" "/c" "dir") ;; No `ls` or `pwd` in cmd. 

;; (I first learned about the need for command flags like "/c" here: 
;; https://stackoverflow.com/a/4031412/2596132

;; These Microsoft docs explain the "/c" flag: 
;; https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/cmd

;; I learned of bash's "-c" flag after finding `exec` in `bash -c help` as suggested
;; from `bash --help. I didn't know that `-c` was the command flag at the time.)

;; To use pipes and whatnot, a simple way is to run eg `bash -c` as the command
;; and the rest as a single string
(clojure.java.shell/sh "/bin/bash" "-c" "ls -la | grep foo")