[ruby] Implement bglist and bgkill

ruby/shell/builtins.rb

@@ -28,6 +28,28 @@ module Shell
       job_control.exec_command(cmd, args, background: true)
     end
 
+    def builtin_bglist(_args)
+      jobs = job_control.list
+      puts unless jobs.empty?
+      jobs.each do |job|
+        puts job_control.format_job(job)
+      end
+      plural = jobs.count == 1 ? '' : 's'
+      puts "#{jobs.count} background job#{plural}"
+      0
+    end
+
+    def builtin_bgkill(args)
+      if args.count != 1
+        logger.warn 'Usage: bgkill <job>'
+        return -1
+      end
+
+      job_id = args.shift.to_i
+      job_control.kill(job_id)
+      0
+    end
+
     def builtin_cd(args)
       Dir.chdir args.first
       0

ruby/shell/job_control.rb

@@ -15,24 +15,6 @@ module Shell
       @logger = logger || Logger.instance
     end
 
-    def trap_sigchld
-      # handler for SIGCHLD when a child's state changes
-      Signal.trap('CHLD') do |_signo|
-        pid = Process.waitpid(-1, Process::WNOHANG)
-        if pid.nil?
-          # no-op
-        elsif (job = @jobs_by_pid[pid])
-          time = Time.now.strftime('%T')
-          job_text = yellow('job ', job.id, ' exited')
-          args = job.args.inspect
-          puts "\n[#{time}] #{job_text} #{white('(pid ', pid, ')')}: #{green(job.cmd)} #{args}"
-        else
-          warn "\n#{yellow('[WARN]')} No job found for child with PID #{pid}"
-        end
-        Readline.refresh_line
-      end
-    end
-
     def exec_command(cmd, args, background: false)
       unless (path = resolve_executable(cmd))
         warn "#{red('[ERROR]')} command not found: #{cmd}"
@@ -61,6 +43,46 @@ module Shell
       -5
     end
 
+    def kill(job_id)
+      job = @jobs_by_pid.values.detect { |j| j.id == job_id }
+      if job.nil?
+        logger.warn "No job found with ID #{job_id}"
+        return
+      end
+
+      Process.kill('TERM', job.pid)
+    rescue Errno::ESRCH
+      logger.warn "No such proccess: #{job.pid}"
+    end
+
+    def list
+      @jobs_by_pid.values.sort_by(&:id)
+    end
+
+    def format_job(job)
+      args = job.args.join(' ')
+      "#{yellow(job.id)}: #{white('(pid ', job.pid, ')')} #{green(job.cmd)} #{args}"
+    end
+
+    def trap_sigchld
+      # handler for SIGCHLD when a child's state changes
+      Signal.trap('CHLD') do |_signo|
+        pid = Process.waitpid(-1, Process::WNOHANG)
+        if pid.nil?
+          # no-op
+        elsif (job = @jobs_by_pid[pid])
+          @jobs_by_pid.delete(pid)
+          time = Time.now.strftime('%T')
+          job_text = yellow('job ', job.id, ' exited')
+          args = job.args.join(' ')
+          puts "\n[#{time}] #{job_text} #{white('(pid ', job.pid, ')')}: #{green(job.cmd)} #{args}"
+        else
+          warn "\n#{yellow('[WARN]')} No job found for child with PID #{pid}"
+        end
+        Readline.refresh_line
+      end
+    end
+
     # Return absolute and relative paths directly, or searches PATH for a
     # matching executable with the given filename and returns its path.
     # Returns nil when no such command was found.