$Id: date-of-file.txt 26 2009-03-13 16:17:35Z j-waldby $

date-of-file is a yume example with -iv value-fields that set commands
using three -la parameters.

date-of-file also illustrates some %x execution modes --
%#, %%, %+, %-, and %:.  These appear in -do groups, so 
that you can clearly see the commands and can change them.

The 3-la -iv form is like:

   -la command -la varname -la displaylabel -iv initvalue


With line-by-line explanations enclosed in brackets [],
date-of-file works as follows:

yume  -ti 'Display Date of File'\
  [Set menu window title to 'Display Date of File']

 -bu -la 'Enter a file name and click button' true\
  [Make a button with label 'Enter a file name and click button'
   and action "true", which is like a no-op.]

 -bu -la 'echo "Date of $FF is `date -r $FF`"'   -la FF -la File: -iv $0\
  [Stack 3 items for command, varname, and displaylabel;
   then make a value field whose value is $0, the script name.]

 -bu -la '%%echo "Date of $FF is `date -r $FF`"' -la FF -la File: -iv $0\
  [Like previous command, except that leading %% cause yume to display
   the command before executing it.  It is displayed without the %%
   showing.  A code like "Y12:" will display also, giving the item
   number of the button or do group that started the command.]

 -bu -ex\
  [Put an exit button on a line by itself]

 -do '%#echo "Date of $FF is `date -r $FF`"'\
  [ %# echoes a command without executing it.]

 -do '%%echo "Date of $FF is `date -r $FF`"'\
  [ %% echoes a command and then executes it.]

 -do '%+echo "Date of $FF is `date -r $FF`"'\
  [ %+ executes command without forking; that is,
    exits from yume and executes command.]

 -do '%-/bin/sh -c "echo Date of $FF is `date -r $FF`"'\
  [ %- executes command without forking or usual shell; 
    that is, exits from yume and executes command as
    expanded by wordexp without going to usual $SHELL.]

 -do '%:/bin/sh -c "echo Date of $FF is `date -r $FF`"'&
  [ %: executes command without usual shell; that is, executes
    command as expanded by wordexp without going to usual $SHELL.]