examples: Process examples (#8598)

examples/process/process_script.v

@@ -0,0 +1,59 @@
+module main
+
+import os
+
+// a test where we execute a bash script but work around where we put script in bash inside bash
+
+fn exec(path string, redirect bool) {
+	mut line := ''
+	mut line_err := ''
+	mut cmd := os.new_process('/bin/bash')
+
+	if redirect {
+		cmd.set_args(['-c', '/bin/bash /tmp/test.sh 2>&1'])
+	} else {
+		cmd.set_args([path])
+	}
+
+	cmd.set_redirect_stdio()
+	cmd.run()
+	if cmd.is_alive() {
+		for {
+			line = cmd.stdout_read()
+			println('STDOUT: $line')
+
+			if !redirect {
+				line_err = cmd.stderr_read()
+				println('STDERR: $line_err')
+			}
+
+			if !cmd.is_alive() {
+				break
+			}
+		}
+	}
+	if cmd.code > 0 {
+		println('ERROR:')
+		println(cmd)
+		// println(cmd.stderr_read())
+	}
+}
+
+fn main() {
+	script := '
+echo line 1
+#will use some stderr now
+echo redirect 1 to 2  1>&2
+echo line 3
+'
+
+	os.write_file('/tmp/test.sh', script) or { panic(err) }
+	// os.chmod("/tmp/test.sh",0o700) //make executable
+
+	// this will work because stderr/stdout are smaller than 4096 chars, once larger there can be deadlocks
+	// in other words this can never work reliably without being able to check if there is data on stderr or stdout
+	exec('/tmp/test.sh', false)
+
+	// this will always work
+	exec('/tmp/test.sh', true)
+}