The Minibuffer

The Minibuffer

When you issue an M-x or C-x command that requires some parameter, emacs will display the command in the minibuffer at the bottom of the screen, and move the cursor there, waiting for your input of the parameter.

Loading Files

As mentioned earlier, the command C-x C-f will prompt you for a file name, create a new buffer, and load the file into that new buffer. Here are some more details, illustrated with an actual example.

I typed C-x C-f. Emacs responded by displaying the following message in the minibuffer:

Find file: ~/tmp/tmp/

I was currently in the directory indicated, i.e. tmp/tmp. I knew that the file I wanted began with the string `Sum', but didn't remember the rest, so I took advantage of emacs's name completion feature: I hit the Space bar, resulting in emacs creating and displaying a buffer named *Completions*, with contents

Possible completions are:
Sum                                Sum.c
Sum.lst                            Sum.mas
Sum.out                            Sum.sym

which was a list of all files in that directory whose names began with `Sum'. I saw that the file I wanted was Sum.mas, so I typed `.m' and then hit the Space bar, so that the minibuffer now looked like

Find file: ~/tmp/tmp/Sum.mas

That is what I wanted, so I hit the Return key, and emacs then loaded the file.

If I had wanted to switch to another directory, I could have backspaced in the minibuffer, erasing part or all of the path displayed there.

Note that this is useful not just if you have forgotten a file name, but also to save typing.

Windows

As mentioned before, a very nice feature of emacs is the ability to split a given buffer into two or more windows, enabling one to view more than one piece of a file at a time. Here are the main commands:

C-x 2    split current window into two windows
C-x o    move cursor to the other window
C-x 1    unsplit, i.e. change back to having just one window on
         this buffer
C-x 0    move cursor to the other window and make that one fill
         the screen (same as C-x o followed by C-x 1)
C-x ^    make current window larger (and other window smaller)

For example, suppose I currently just have one window on my WC.c buffer in the example above. If I type C-x 2, the result will be:

/* introductory C program */

/* implements (a subset of) the Unix wc command  --  reports character,
   word and line counts; in this version, the "file" is read from the
   standard input, since we have not covered C file manipulation yet,





/* introductory C program */

/* implements (a subset of) the Unix wc command  --  reports character,
   word and line counts; in this version, the "file" is read from the
   standard input, since we have not covered C file manipulation yet,
   but of course a real file can be read by using the Unix `<' redirection

Now I can scroll the two windows independently. For example, suppose I want one window to show the function WordCount(), and the other window to show the call to that function. What I can do is use the vi search command `/' to look for the string `WordCount', and thus position the two windows as desired:

int WordCount()

{  int I,NBlanks = 0;

   for (I = 0; I < LineLength; I++)
      if (Line[I] == ' ') NBlanks++;

   /* ordinarily the number of words is NBlanks+1, except in the case
      in which the line is empty, i.e. consists only of the end-of-line
      character */

      Line[LineLength++] = C;
      if (C == 10) break;
   }

   NChars += LineLength;
   NWords += WordCount();
   NLines++;
   return 0;
}