# 7.14 Script watching: pyxplot_watch

Pyxplot includes a simple tool for watching command script files and executing them whenever they are modified. This may be useful when developing a command script, if one wants to make small modifications to it and see the results in a semi-live fashion. This tool is invoked by calling the `pyxplot_watch` command from a shell prompt. The command-line syntax of `pyxplot_watch` is similar to that of Pyxplot itself, for example:

    pyxplot_watch script.ppl

would set `pyxplot_watch` to watch the command script file `script.ppl`. One difference, however, is that if multiple script files are specified on the command line, they are watched and executed independently, not sequentially, as Pyxplot itself would do. Wildcard characters can also be used to set `pyxplot_watch` to watch multiple files.1

This is especially useful when combined with ghostview’s watch facility. For example, suppose that a script `foo.ppl` produces PostScript output `foo.ps`. The following two commands could be used to give a live view of the result of executing this script:

    gv --watch foo.ps &
    pyxplot_watch foo.ppl

Footnotes

1. Note that `pyxplot_watch *.script` and `pyxplot_watch *.script` will behave differently in most UNIX shells. In the first case, the wildcard is expanded by your shell, and a list of files passed to `pyxplot_watch`. Any files matching the wildcard, created after running `pyxplot_watch`, will not be picked up. In the latter case, the wildcard is expanded by `pyxplot_watch` itself, which will pick up any newly created files.