This document describes how to use JED in its non-interactive mode.  It
assumes that the reader is reasonably familiar with S-Lang programming for
JED. 

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In a very real sense, JED is a text processing utility that operates in two
modes: interactive mode and non-interactive or BATCH mode.  One example of
using JED in batch mode is:

   jed -batch -l preparse.sl
   
JED will run non-interactively only if the command line parameter is
`-batch'.   For example, 

    % jed -batch -f quit_jed
    loading /usr/local/jed/lib/site.slc
    loading /usr/local/jed/lib/os.sl
    loading /usr1/users/davis/.jedrc

Notice that this is very noisy since it displays all the files that it is
loading. There is a quieter non-interactive form that is specified by using
`-script' instead of `-batch'.  The syntax for this parameter is:

   jed -script script-file [arg] ....

The `-script' parameter functions exactly like the `-l' (load file)
parameter except that 

   1.  It runs in non-interactive mode.

   2.  The rest of the command line arguments (arg) are not parsed.  It is
       up to the code in the script file to parse the remaining arguments if
       they are present.
       
   3.  The user's .jedrc (jed.rc) file is NOT loaded.  To load it, add the
       appropriate `evalfile' to the script.

It is best to provide an example, although silly.  This example script
writes simply counts the number of lines in the files specified on the
command line and writes the value on stdout.

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static variable i = 3;
static variable count = 0;
if (__argc <= 3)
  {
     message ("Usage: jed -script count-lines.sl file ...");
     quit_jed ();
  }
  
while (i < __argc)
{
   () = read_file (__argv[i]);
   eob ();
   count += what_line ();
   if (bolp ()) count--;
   delbuf (whatbuf());
   i++;
}

vmessage ("%d lines", count);
quit_jed ();
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Note the following points:

   1. When the script file is loaded, the NEXT command line argument to 
      be evaluated is 3.

   2. The global variable __argc contains the number of command line
      arguments.  The command line arguments are contained in the
      array __argv.  Since the arguments are numbered from 0, the last
      one is number __argc - 1. The ith command line argument is given
      by __argv[i].   For this particular example, the __argv array
      will consist of:
      
            __argv[0] = "jed"
            __argv[1] = "-script"
	    __argv[2] = "count-lines.sl";
	    __argv[3] = the name of the file to be processed

   3. `quit_jed' is called to exit the editor.  `exit_jed' could also be
      used when it is necessary to run the exit hooks.
      
To exectute this script, type:

   % jed -script count-lines.sl 
   
It should display the usage message.

Unix also provides a mechanism for making any script file an executable
file.  The trick is to add the appropriate line to the top of the script and
change the permissions on the script to make it executable.  In this case,
do the following:

    1. Add:
    
         #!/usr/bin/env jed-script
      
       to the top of the file.  The /usr/bin/env program is used
       because some operating systems put a limit on the number of
       characters allowed in this line.
       
       Note also "jed-script" is used.  Here jed-script is a assumed
       to be a symbolic link to jed.
       
    2. At the unix prompt, enter:  chmod +x count-lines.sl

As a final example, consider a script file that may be used in DOS batch
files to replace strings in files, e.g., to replace all occurances of `x'
with `y' in `C:\windows\win.ini'.  If such a script file is called
`change.sl', it could be used as:

    jed -script change.sl C:\windows\win.ini x y
    
A script file that performs this task is:

   % change.sl
   
   if (__argc != 6)
     {
        message ("Usage: jed -script change.sl file old-string new-string");
        quit_jed ();
     }
  
   () = read_file (__argv[3]);
   replace (__argv[4], __argv[5]);
   save_buffer ();
   quit_jed ();