1 ED Tutorial 10/28/80 ED Tutorial A Tutorial Introduction to the Software Tools TEXT EDITOR B. Kernighan Bell Laboratories and M.J. Gralia Johns Hopkins University - Applied Physics Laboratory INTRODUCTION E + E + Ed + d + d is a "text editor", that is, an interactive program for creating and modifying "text", using directions provided by a user at a terminal. The text is often a document like this one, or a program or perhaps data for a program. This introduction is meant to simplify learning e + e + ed + d + d. + . + . The recommended way to learn e + e + ed + d + d is to read this document, simultaneously using e + e + ed + d + d to follow the examples, then to read the description in section I of the Software Tools manual, all the while experimenting with e + e + ed + d + d. + . + . (Solicitation of advice from experienced users is also useful.) Do the exercises! They cover material not completely discussed in the actual text. An appendix summarizes the commands. DISCLAIMER This is an introduction and a tutorial. For this reason, no attempt is made to cover more than a part of the facilities that e + e + ed + d + d offers (although this fraction includes the most useful and frequently used parts). Also, there is not enough space to explain basic Software Tools procedures. We will assume that you know how to log on and access the Software Tools, and that you have at least a vague understanding of what a file is. You must also know what character to type as the end-of-line on your particular terminal. It is almost always a "return". Throughout, we will refer to this character, whatever it is, as "newline". CASES And about case: it is traditional to use both upper and lower case characters when using the Software Tools, but it -1- 1 ED Tutorial 10/28/80 ED Tutorial is not required. In describing e + e + ed + d + d, + , + , we will follow that convention, but e + e + ed + d + d will work with either. But a caution: e + e + ed + d + d differentiates cases. If your files contain both and your terminal is in upper case, you can get into a "deadly embrace" situation in which you can see a character but can't delete it. The solution is simple - always use both upper and lower case with Software Tools. GETTING STARTED We'll assume that you have logged in. The easiest way to get e + e + ed + d + d is to type ed (followed by a newline) You are now ready to go - e + e + ed + d + d is waiting for you to tell it what to do. CREATING TEXT - the Append command ``a'' As our first problem, suppose we want to create some text starting from scratch. Perhaps we are typing the very first draft of a paper; clearly it will have to start somewhere, and undergo modifications later. This section will show how to get some text in, just to get started. Later we'll talk about how to change it. When e + e + ed + d + d is first started, it is rather like working with a blank piece of paper - there is no text or information present. This must be supplied by the person using e + e + ed + d + d; + ; + ; it is usually done by typing in the text, or by reading it into e + e + ed + d + d from a file. We will start by typing in some text, and return shortly to how to read files. First a bit of terminology. In e + e + ed + d + d jargon, the text being marked on is said to be "kept in a buffer." Think of the buffer as a work space, if you like, or simply as the information that you are going to be editing. In effect the buffer is like the piece of paper on which we will write things, then change some of them, and finally file the whole thing away for another day. The user tells e + e + ed + d + d what to do to his text by typing instructions called "commands". Most commands consist of a single letter. Each command is typed on a separate line. (Sometimes the command is preceded by information about what line or lines of text are to be affected - we will discuss these shortly.) The first command is a + a + ap + p + pp + p + pe + e + en + n + nd + d + d, + , + , written as the letter a -2- 1 ED Tutorial 10/28/80 ED Tutorial all by itself. It means " + " + "a + a + ap + p + pp + p + pe + e + en + n + nd + d + d (or add) text lines to the buffer, as I type them in." Appending is rather like writing fresh material on a piece of paper. So to enter lines of text into the buffer, we just type an "a" followed by a newline, followed by the lines of text we want, like this: a Now is the time for all good men to come to the aid of their party. . The only way to stop appending is to type a line that contains only a period. The "." is used to tell e + e + ed + d + d that we have finished appending. (Even experienced users forget that terminating "." sometimes. If e + e + ed + d + d seems to be ignoring you, type an extra line with just "." on it. You may then find you've added some garbage lines to your text, which you'll have to take out later.) After the append command has been done, the buffer will contain the three lines Now is the time for all good men to come to the aid of their party. The "a" and "." aren't there, because they are not text. To add more text to what we already have, just issue another "a" command, and continue typing. (Try it now - it won't always work right until we explain about line numbers.) ERROR MESSAGES - ``?'' If at any time you make an error in the commands you type to e + e + ed + d + d, + , + , it will tell you by typing ? This is about as cryptic as it can be, but with practice, you can usually figure out how you goofed. WRITING TEXT OUT AS A FILE - the Write command ``w'' It's likely that we'll want to save our text for later use. To write out the contents of the buffer onto a file, we use the w + w + wr + r + ri + i + it + t + te + e + e command w -3- 1 ED Tutorial 10/28/80 ED Tutorial followed by the filename we want to write on. This will copy the buffer's contents onto the specified file (destroying any previous information on the file). To save the text on a file named "junk", for example, type w junk Leave a space between "w" and the file name. E + E + Ed + d + d will respond by printing the number of lines it wrote out. In our case, e + e + ed + d + d would respond with 3 Writing a file just makes a copy of the text - the buffer's contents are not disturbed, so we can go on adding lines to it. This is an important point. E + E + Ed + d + d at all times works on a copy of a file, not the file itself. No change in the contents of a file takes place until you give a "w" command. (Writing out the text onto a file from time to time as it is being created is a good idea, since if the system crashes or if you make some horrible mistake, you will lose all the text in the buffer, but any text that was written onto a file is relatively safe.) LEAVING ED - the Quit command ``q'' To terminate a session with e + e + ed + d + d, + , + , save the text you're working on by writing it onto a file using the "w" command, and then type the command q which stands for q + q + qu + u + ui + i + it + t + t. + . + . At this point your buffer vanishes, with all its text, which is why you want to write it out before quitting. EXERCISE 1: Enter e + e + ed + d + d and create some text using a ...text... . Write it out using "w". Then leave e + e + ed + d + d with the "q" command, and print the file, to see that everything worked. (To print a file, say cat filename Also try crt filename -4- 1 ED Tutorial 10/28/80 ED Tutorial Here, you need to enter a newline (to see the next page) or "q" (to quit displaying the text). READING TEXT FROM A FILE - the Edit command ``e'' A common way to get text into the buffer is to read it from a file in the file system. This is what you do to edit text that you saved with the "w" command in a previous session. The e + e + ed + d + di + i + it + t + t command "e" fetches the entire contents of a file into the buffer. So if we had saved the three lines "Now is the time", etc., with a "w" command in an earlier session, the e + e + ed + d + d command e junk would fetch the entire contents of the file "junk" into the buffer, and respond 3 which is the number of lines in "junk". If anything was already in the buffer, it is deleted first. If we use the "e" command to read a file into the buffer, then we need not use a file name after a subsequent "w" command; e + e + ed + d + d remembers the last file name used in an "e" command, and "w" will write on this file. Thus a common way to operate is ed e file [editing session] w q You can find out at any time what file named e + e + ed + d + d is remembering by typing the f + f + fi + i + il + l + le + e + e command "f". In our case, if we typed f e + e + ed + d + d would reply junk READING TEXT FROM A FILE - the Read command ``r'' Sometimes we want to read a file into the buffer without destroying anything that is already there. This is done by the r + r + re + e + ea + a + ad + d + d command "r". The command r junk -5- 1 ED Tutorial 10/28/80 ED Tutorial will read the file "junk" into the buffer; it adds it to the buffer (after the current line). So if we do a read after an edit: e junk r junk the buffer will contain t + t + tw + w + wo + o + o copies of the text (six lines). Now is the time for all good men to come to the aid of their party. Now is the time for all good men to come to the aid of their party. Like the "w" and "e" commands, "r" prints the number of newlines read in, after the reading operation is complete. Generally speaking, "r" is much less used than "e". EXERCISE 2: Experiment with the "e" command - try reading and printing various files. You may get an error "?.", typically because you spelled the file name wrong. Try alternately reading and appending to see that they work similarly. Verify that ed filename is exactly equivalent to ed e filename What does f filename do? PRINTING THE CONTENTS OF THE BUFFER - the Print command ``p'' To p + p + pr + r + ri + i + in + n + nt + t + t or list the contents of the buffer (or parts of it) on the terminal, we use the print command p The way this is done is as follows. We specify the lines where we want printing to begin and where we want it to end, separated by a comma, and followed by the letter "p". Thus to print the first two lines of the buffer, for example, (that is, lines 1 through 2) we say -6- 1 ED Tutorial 10/28/80 ED Tutorial 1,2p (starting line=1, ending line=2) E + E + Ed + d + d will respond with Now is the time for all good men Suppose we want to print a + a + al + l + ll + l + l the lines in the buffer. We could use "1,3p" as above if we knew there were exactly 3 lines in the buffer. But in general, we don't know how many there are so what do we use for the ending line number? E + E + Ed + d + d provides a shorthand symbol for "line number of last line in buffer" - the dollar sign "$". Use it this way: 1,$p This will print a + a + al + l + ll + l + l the lines in the buffer (line 1 to the last line.) To print the l + l + la + a + as + s + st + t + t line of the buffer, we could use $,$p but e + e + ed + d + d lets us abbreviate this to $p We can print any single line by typing the line number followed by a "p". Thus 1p produces the response Now is the time which is the first line of the buffer. In fact, e + e + ed + d + d lets us abbreviate even further: we can print any single line by typing j + j + ju + u + us + s + st + t + t the line number - no need to type the letter "p". So if we say $ e + e + ed + d + d will print the last line of the buffer for us. We can also use "$" in combinations like $-1,$p which prints the last two lines of the buffer. This helps -7- 1 ED Tutorial 10/28/80 ED Tutorial when we want to see how far we got in typing. EXERCISE 3: As before, create some text using the append command and experiment with the "p" command. You will find, for example, that you can't print line 0 or a line beyond the end of the buffer, and that attempts to print a buffer in reverse order by saying 3,1p don't work. THE CURRENT LINE - 'Dot' or '.' Suppose our buffer still contains the six lines as above, that we have just typed 1,3p and e + e + ed + d + d has printed the three lines for us. Try typing just p (no line numbers). This will print to come to the aid of their party. which is the third line of the buffer. In fact it is the last (most recent) line that we have done anything with. (We just printed it!) We can repeat this "p" command without line numbers, and it will continue to print line 3. The reason is that e + e + ed + d + d maintains a record of the last line that we did anything to (in this case, line 3, which we just printed) so that it can be used instead of an explicit line number. This most recent line is referred to by the shorthand symbol . (pronounced "dot"). Dot is a line number in the same way that "$" is; it means exactly "the current line", or loosely, "the line we most recently did something to." We can use it in several ways - one possibility is to say .,$p This will print all the lines from (including) the current line to the end of the buffer. In our case these are lines 3 through 6. -8- 1 ED Tutorial 10/28/80 ED Tutorial Some commands change the value of dot, while others do not. The print command sets dot to the number of the last line printed; by our last command, we would have "." = "$" = 6. Dot is most useful when used in combinations like this one: .+1 (or equivalently, .+1p) This means "print the next line" and gives us a handy way to step slowly through a buffer. We can also say .-1 (or .-1p) which means "print the line b + b + be + e + ef + f + fo + o + or + r + re + e + e the current line." This enables us to go backwards if we wish. Another useful one is something like .-3,.-1p which prints the previous three lines. Don't forget that all of these change the value of dot. You can find out what dot is at any time by typing .= E + E + Ed + d + d will respond by printing the value of dot. Let's summarize some things about the "p" command and dot. Essentially "p" can be preceded by 0, 1, or 2 line numbers. If there is no line number given, it prints the "current line", the line that dot refers to. If there is one line number given (with or without the letter "p"), it prints that line (and dot is set there); and if there are two line numbers, it prints all the lines in that range (and sets dot to the last line printed.) If two line numbers are specified the first can't be bigger than the second (see Exercise 3.) Typing a single newline will cause printing of the next line - it's equivalent to ".+1p". Try it. DELETING LINES: the ``d'' command Suppose we want to get rid of the three extra lines in the buffer. This is done by the d + d + de + e + el + l + le + e + et + t + te + e + e command d Except that "d" deletes lines instead of printing them, its action is similar to that of "p". The lines to be deleted are specified for "d" exactly as they are for "p": -9- 1 ED Tutorial 10/28/80 ED Tutorial starting-line, ending-line d Thus the command 4,$d deletes lines 4 through the end. There are now three lines left, as we can check by using 1,$p And notice that "$" now is line 3! Dot is set to the next line after the last line deleted, unless the last line deleted is the last line in the buffer. In that case, dot is set to "$". EXERCISE 4: Experiment with "a", "e", "r", "w", "p", and "d" until you are sure that you know what they do, and until you understand how dot, "$", and line numbers are used. If you are adventurous, try using line numbers with "a", "r", and "w" as well. You will find that "a" will append lines a + a + af + f + ft + t + te + e + er + r + r the line number that you specify (rather than after dot); that "r" reads a file in a + a + af + f + ft + t + te + e + er + r + r the line number you specify (not necessarily at the end of the buffer); and that "w" will write out exactly the lines you specify, not necessarily the whole buffer. These variations are sometimes handy. For instance you can insert a file at the beginning of a buffer by saying 0r filename and you can enter lines at the beginning of the buffer by saying 0a ...text... . Notice that ".w" is v + v + ve + e + er + r + ry + y + y different from . w MODIFYING TEXT: the Substitute command ``s'' We are now ready to try one of the most important of all commands - the substitute command s -10- 1 ED Tutorial 10/28/80 ED Tutorial This is the command that is used to change individual words or letters within a line or group of lines. It is what we use, for example, for correcting spelling mistakes and typing errors. Suppose that by a typing error, line 1 says Now is th time - the "e" has been left off "the". We can use "s" to fix this up as follows: 1s/th/the/ This says: "in line 1, substitute for the characters `th' the characters `the'. To verify that it works ( e + e + ed + d + d will not print the result automatically) we say p and get Now is the time which is what we wanted. Notice that dot must have been set to the line where the substitution took place, since the "p" command printed that line. Dot is always set this way with the "s" command. The general way to use the substitute command is starting-line, ending-line s/change this/to this/ Whatever string of characters is between the first pair of slashes is replaced by whatever is between the second pair, in a + a + al + l + ll + l + l the lines between starting line and ending line. Only the first occurrence on each line is changed, however. If you want to change e + e + ev + v + ve + e + er + r + ry + y + y occurrence, see Exercise 5. The rules for line numbers are the same as those for "p", except that dot is set to the last line changed. (But there is a trap for the unwary: if no substitution took place, dot is n + n + no + o + ot + t + t changed. This causes an error "?" as a warning.) Thus we can say 1,$s/speling/spelling/ and correct the first spelling mistake on each line in the text. (This is useful for people who are consistent misspellers!) -11- 1 ED Tutorial 10/28/80 ED Tutorial If no line numbers are given, the "s" command assumes we mean "make the substitution on line dot", so it changes things only on the current line. This leads to the very common sequence s/something/something else/p which makes some correction on the current line, and then prints it, to make sure it worked out right. If it didn't, we can try again. (Notice that we put a print command on the same line as the substitute. With few exceptions, "p" can follow any command; no other multi-command lines are legal.) It's also legal to say s/something// which means "change 'something' to n + n + no + o + ot + t + th + h + hi + i + in + n + ng + g + g, + , + ," + " + " i.e., remove it. This is useful for deleting extra words in a line or removing extra letters from words. For instance, if we had Nowxx is the time we can say s/xx//p to get Now is the time Notice that "//" here means "no characters", not a blank. There i + i + is + s + s a difference! (See below for another meaning of "//".) EXERCISE 5: Experiment with the substitute command. See what happens if you substitute for some word on a line with several occurrences of that word. For example, do this: a the other side of the coin . s/the/on the/p You will get on the other side of the coin A substitute command changes only the first occurrence of -12- 1 ED Tutorial 10/28/80 ED Tutorial the first string. You can change all occurrences by adding a "g" (for "global") to the "s" command, like this: s/.../.../gp Try other characters instead of slashes to delimit the two sets of characters in the "s" command - anything should work except blanks or tabs. (If you get funny results using any of the characters % ? $ [ * read the section on "Special Characters".) CONTEXT SEARCHING - ``/.../'' With the substitute command mastered, we can move on to another highly important idea of e + e + ed + d + d - context searching. Suppose we have our original three line text in the buffer: Now is the time for all good men to come to the aid of their party. Suppose we want to find the line that contains "their" so we can change it to "the". Now with only three lines in the buffer, it's pretty easy to keep track of what line the word "their" is on. But if the buffer contained several hundred lines, and we'd been making changes, deleting and rearranging lines, and so on, we would no longer really know what this line number would be. Context searching is simply a method of specifying the desired line, regardless of what its number is, by specifying some context on it. The way we say "search for a line that contains this particular string of characters" is to type /string of characters we want to find/ For example, the e + e + ed + d + d line /their/ is a context search which is sufficient to find the desired line - it will locate the next occurrence of the characters between slashes ("their"). It also sets dot to that line and prints the line for verification: to come to the aid of their party. -13- 1 ED Tutorial 10/28/80 ED Tutorial "Next occurrence" means that e + e + ed + d + d starts looking for the string at line ".+1", searches to the end of the buffer, then continues at line 1 and searches to line dot. (That is, the search "wraps around" from "$" to 1.) It scans all the lines in the buffer until it either finds the desired line or gets back to dot again. If the given string of characters can't be found in any line, e + e + ed + d + d types the error message ? Otherwise it prints the line it found. We can do both the search for the desired line a + a + an + n + nd + d + d a substitution all at once, like this: /their/s/their/the/p which will yield to come to the aid of the party. There were three parts to that last command: context search for the desired line, make the substitution, print the line. The expression "/their/" is a context search expression. In their simplest form, all context search expressions are like this - a string of characters surrounded by slashes. Context searches are interchangeable with line numbers, so they can be used by themselves to find and print a desired line, or as line numbers for some other command, like "s". We used them both ways in the examples above. Suppose the buffer contains the three familiar lines Now is the time for all good men to come to the aid of their party. Then the e + e + ed + d + d line numbers /Now/+1 /good/ /party/-1 are all context search expressions, and they all refer to the same line (line 2). To make a change in line 2, we could say /Now/+1s/good/bad/ -14- 1 ED Tutorial 10/28/80 ED Tutorial or /good/s/good/bad/ or /party/-1s/good/bad/ The choice is dictated only by convenience. We could print all three lines by, for instance /Now/,/party/p or /Now/,/Now/+2p or by any number of similar combinations. The first one of these might be better if we don't know how many lines are involved. (Of course, if there were only three lines in the buffer, we could use 1,$p but not if there were several hundred.) The basic rule is: a context search expression is t + t + th + h + he + e + e same as a line number, so it can be used wherever a line number is needed. EXERCISE 6: Experiment with context searching. Try a body of text with several occurrences of the same string of characters, and scan through it using the same context search. Try using context searches as line numbers for the substitute, print and delete commands. (They can also be used with "r", "w", and "a".) Try context searching using "\text\" instead of "/text/". This scans lines in the buffer in reverse order rather than normal. This is sometimes useful if you go too far while looking for some string of characters - it's an easy way to back up. (If you get funny results with any of the characters % ? $ [ * read the section on "Special Characters".) -15- 1 ED Tutorial 10/28/80 ED Tutorial E + E + Ed + d + d provides a shorthand for repeating a context search for the same string. For example, the e + e + ed + d + d line number /string/ will find the next occurrence of "string". It often happens that this is not the desired line, so the search must be repeated. This can be done by typing merely // This shorthand stands for "the most recently used context search expression." It can also be used as the first string of the substitute command, as in /string1/s//string2/ which will find the next occurrence of "string1" and replace it by "string2". This can save a lot of typing. Similarly \\ means "scan backwards for the same expression." CHANGE and INSERT - ``c'' and ``i'' This section discusses the c + c + ch + h + ha + a + an + n + ng + g + ge + e + e command c which is used to change or replace a group of one or more lines, and the i + i + in + n + ns + s + se + e + er + r + rt + t + t command i which is used for inserting a group of one or more lines. "Change", written as c is used to replace a number of lines with different lines, which are typed in at the terminal. For example, to change lines ".+1" through "$" to something else, type .+1,$c ...type the lines of text you want here... . The lines you type between the "c" command and the "." will take the place of the original lines between start line and end line. This is most useful in replacing a line or -16- 1 ED Tutorial 10/28/80 ED Tutorial several lines which have errors in them. If only one line is specified in the "c" command, then just that line is replaced. (You can type in as many replacement lines as you like.) Notice the use of "." to end the input - this works just like the "." in the append command and must appear by itself on a new line. If no line number is given, line dot is replaced. The value of dot is set to the last line you typed in. "Insert" is similar to append - for instance /string/i ...type the lines to be inserted here... . will insert the given text b + b + be + e + ef + f + fo + o + or + r + re + e + e the next line that contains "string". The text between "i" and "." is i + i + in + n + ns + s + se + e + er + r + rt + t + te + e + ed + d + d before the specified line. If no line number is specified dot is used. Dot is set to the last line inserted. EXERCISE 7: "Change" is rather like a combination of delete followed by insert. Experiment to verify that start, end d i ...text... . is almost the same as start, end c ...text... . These are not p + p + pr + r + re + e + ec + c + ci + i + is + s + se + e + el + l + ly + y + y the same if line "$" gets deleted. Check this out. What is dot? Experiment with "a" and "i", to see that they are similar, but not the same. -17- 1 ED Tutorial 10/28/80 ED Tutorial You will observe that line-number a ...text.. . appends a + a + af + f + ft + t + te + e + er + r + r the given line, while line-number i ...text... . inserts b + b + be + e + ef + f + fo + o + or + r + re + e + e it. Observe that if no line number is given, "i" inserts before line dot, while "a" appends after line dot. BROWSING: the ``b'' command Many times you want to look at several lines of a large file while you're using a video terminal. If you said 1,$p the whole buffer would flash on the screen, usually too fast to read. A better way is the browse command "b". It prints just enough lines (23) to fill the CRT screen. Browse has three major forms which control what lines are displayed. "b" or "b+" prints the current line and the screen after it. "b." prints the screen centered on the current line and including it. "b-" prints the screenful before the current line. MOVING TEXT AROUND: the ``m'' command The move command "m" is used for cutting and pasting - it lets you move a group of lines from one place to another on the buffer. Suppose we want to put the first three lines of the buffer at the end instead. We could do it by saying: 1,3w temp $r temp 1,3d (Do you see why?) but we can do it a lot easier with the "m" command: 1,3m$ The general case is start-line, end-line m after-this-line Notice that there is a third line to be specified - the -18- 1 ED Tutorial 10/28/80 ED Tutorial place where the moved stuff gets put. Of course the lines to be moved can be specified by context searches; if we had First paragraph ... end of first paragraph. Second paragraph ... end of second paragraph. we could reverse the two paragraphs like this: /Second/,/second/m/First/-1 Notice the "-1" - the moved text goes a + a + af + f + ft + t + te + e + er + r + r the line mentioned. Dot gets set to the last line moved. THE GLOBAL COMMAND ``g'' The g + g + gl + l + lo + o + ob + b + ba + a + al + l + l command "g" is used to execute an e + e + ed + d + d command on all those lines in the buffer that match some specified string. For example g/peling/p prints all lines that contain "peling". More usefully, g/peling/s//pelling/gp makes the substitution everywhere on the line, then prints each corrected line. Compare this to 1,$s/peling/pelling/gp which only prints the last line substituted. Another subtle difference is that the "g" command does not give a "?" if "peling" is not found where the "s" command will. SPECIAL CHARACTERS You may have noticed that things just don't work right when you used some characters like "?", "*", "$", and others in context searches and the substitute command. The reason is rather complex, although the cure is simple. Basically, e + e + ed + d + d treats these characters as special, with special meanings. For instance, i + i + in + n + n a context search or the first string of the substitute command only, /x?y/ means "a line with an x, a + a + an + n + ny + y + y character, and a y," n + n + no + o + ot + t + t just "a line with an x, a question mark, and a y." A complete list of the special characters that can cause trouble is the -19- 1 ED Tutorial 10/28/80 ED Tutorial following: % . $ [ * @ # ! W + W + Wa + a + ar + r + rn + n + ni + i + in + n + ng + g + g: + : + : The character @ is special to e + e + ed + d + d. + . + . For safety's sake, avoid it where possible. If you have to use one of the special characters in a substitute command, you can turn off its magic meaning temporarily by preceding it with the "at" sign. Thus s/@@@?@*/at quest star/ will change "@?*" into "at quest star". Here is a hurried synopsis of the other special characters. First, the percent "%" signifies the beginning of a line. Thus /%string/ finds "string" only if it is at the beginning of a line: it will find string but not the string... The dollar-sign "$" is just the opposite of the percent sign; it means the end of a line: /string$/ will only find an occurrence of "string" that is at the end of some line. This implies, of course, that /%string$/ will find only a line that contains just "string", and /%?$/ finds a line containing exactly one character. The character "?", as we mentioned above, matches anything; /x?y/ matches any of -20- 1 ED Tutorial 10/28/80 ED Tutorial xay x1y x+y x-y x y x.y This is useful in conjunction with "*", which is a repetition character; "a*" is shorthand for "any number of a's", so "?*" matches any number of anythings. This is used like this: s/?*/stuff/ which changes an entire line, or s/?*,// which deletes all characters in the line up to and including the last comma. (Since "?*" finds the longest possible match, this goes up to the last comma.) "[" is used with "]" to form "character classes"; for example, /[1234567890]/ matches any single digit - any one of the characters inside the braces will cause a match. Finally, the "&" is another shorthand character - it is used only on the right-hand part of a substitute command where it means "whatever was matched on the left-hand side". It is used to save typing. Suppose the current line contained Now is the time and we wanted to put parentheses around it. We could just retype the line, but this is tedious. Or we could say s/%/(/ s/$/)/ using our knowledge of "%" and "$". But the easiest way uses the "&": s/?*/(&)/ This says "match the whole line, and replace it by itself surrounded by parens." The "&" can be used several times in a line; consider using -21- 1 ED Tutorial 10/28/80 ED Tutorial s/?*/&. &!!/ to produce Now is the time. Now is the time!! We don't have to match the whole line, of course: if the buffer contains the end of the world we could type /world/s//& is at hand/ to produce the end of the world is at hand Observe this expression carefully, for it illustrates how to take advantage of e + e + ed + d + d to save typing. The string "/world/" found the desired line; the shorthand "//" found the same word in the line; and the "&" saved us from typing it again. The "&" is a special character only within the replacement text of a substitute command, and has no special meaning elsewhere. We can turn off the special meaning of "&" by preceding it with a "@": s/ampersand/@&/ will convert the word "ampersand" into the literal symbol "&" in the current line. ACKNOWLEDGEMENT The majority of this document has been taken, with the author's permission, from "A Tutorial Introduction to the UNIX Text Editor" by B. W. Kernighan. It has been changed only to reflect the differences between this editor and the UNIX version. SUMMARY OF COMMANDS AND LINE NUMBERS The general form of e + e + ed + d + d commands is the command name, perhaps preceded by one or two line numbers, and, in the case of e + e + e, + , + , r + r + r and w + w + w, + , + , followed by a file name. Only one command is allowed per line, but a p + p + p command may follow any other command (except for e + e + e, + , + , r + r + r, + , + , w + w + w and q + q + q) + ) + ). + . + . a + a + a (append) Add lines to the buffer (at line dot, unless a different line is specified). Appending continues until "." is typed on a new line. Dot is set to the last line -22- 1 ED Tutorial 10/28/80 ED Tutorial appended. b + b + b (browse) Display 23 lines of text, beginning at the current line. The current line will be centered if you use b. ("b dot"). Using b- will cause the previous 23 lines to be printed. c + c + c (change) Change the specified lines to the new text which follows. The new lines are terminated by a ".". If no lines are specified, replace line dot. Dot is set to last line changed. d + d + d (delete) Delete the lines specified. If none are specified, delete line dot. Dot is set to the first undeleted line, unless "$" is deleted, in which case dot is set to "$". e + e + e (edit) Edit new file. Any previous contents of the buffer are thrown away, so issue a w + w + w beforehand if you want to save them. f + f + f (file) Print remembered filename. If a name follows f + f + f the remembered name will be set to it. g + g + g (global) g/---/command will execute the command on those lines that contain "---", which can be any context search expression. i + i + i (insert) Insert lines before specified line (or dot) until a "." is typed on a new line. Dot is set to last line inserted. m + m + m (move) Move lines specified to after the line named after m + m + m. + . + . Dot is set to the last line moved. p + p + p (print) Print specified lines. If none specified, print line dot. A single line number is equivalent to "line-number p". A single newline prints ".+1", the next line. q + q + q (quit) Exit from ed. Wipes out all text in buffer!! r + r + r (read) Read a file into buffer (at end unless specified elsewhere.) Dot set to last line read. s + s + s (substitute) s/string1/string2/ will substitute the characters of `string2' for `string1' in specified lines. If no line is specified, make substitution in line dot. Dot is set to last line in which a substitution took place, which means that if no substitution took place, dot is not changed. s + s + s changes only the first occurrence of string1 on a -23- 1 ED Tutorial 10/28/80 ED Tutorial line; to change all of them, type a "g" after the final slash. w + w + w (write) Write out buffer onto a file. Dot is not changed. . + . + .= + = + = (dot value) Print value of dot. ("=" by itself prints the value of "$".) / + / + /- + - + -- + - + -- + - + -/ + / + / Context search. Search for next line which contains this string of characters. Print it. Dot is set to line where string found. Search starts at ".+1", wraps around from "$" to 1, and continues to dot, if necessary. \---\ Context search in reverse direction. Start search at ".-1", scan to 1, wrap around to "$". -24- 1