         if not target?
             target = @base_filename + '.sagetex.sage'
         @_exec
-            command : 'sage'
-            args    : [target]
-            timeout : 45
-            cb      : (err, output) =>
+            command     : 'sage'
+            args        : [target]
+            timeout     : 45
+            allow_post  : false
+            cb          : (err, output) =>
                 if err
                     cb?(err)
                 else

            timeout     : 30
            err_on_exit : false
            bash        : false
            cb          : required
        #console.log(opts.path)
        #console.log(opts.command + ' ' + opts.args.join(' '))

    _run_knitr: (cb) =>
        @_need_to_run ?= {}
        @_exec
            command     : "echo 'require(knitr); opts_knit$set(concordance = TRUE); knit(\"#{@filename_rnw}\")' | R --no-save"
            bash        : true
            timeout     : 60
            allow_post  : false
            cb          : (err, output) =>
                if err
                    cb?(err)
                else
