If you need to read lines from another file into the file you are currently editing within the Vi text editor, you can do so by utilizing the editor's ability to execute an external command, e.g., a Linux/Unix shell command, by entering an exclamation mark followed by the external command. E.g., if I wanted to read the first 55 lines from the file ~/temp/lincoln.txt, I could e nter Vi's colon mode by hitting Esc followed by the colon character. I could then type r, which is the command used to read from another file. But, instead of immediately typing the file name, e.g. :r ~/temp/lincoln.txt, I could use the head utility to read the first fifty-five lines of the file by typing head -55 followed by the path to the file and the file name. E.g.:

:r !head -55 ~/temp/lincoln.txt

If, instead, I wanted to read the last 14 lines of the file, I could use the tail command.

:r !tail -14 ~/temp/lincoln.txt

If I wanted to include specific lines from the other file into the one I'm currently editing, e.g., lines 10 through 15, I could use the sed command as shown below.

:r !sed -n 10,15p ~/temp/lincoln.txt

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To remove all lines containing a particular string in the vi or Vim text editors, you can use the g command to globally search for the specified string and then, by putting a "d" at the end of the command line, specify that you want all lines containing the specified string deleted. E.g., If I wanted to remove all lines containing the string "dog", I could use the following command.

:g/dog/d

That command would also remove any lines containing "dogs", "dogged", etc. If I just wanted to remove lines containing "dog", I could use :g/dog /d.

You can, of course, specify the pattern on which you wish to search using regular expressions. E.g., if I wanted to remove any lines containing either "dog" or "hog", I could use the command below.

g/[dh]og/d

By putting the leters "d" and "h" within brackets, I indicate to vi that it should remove any line that has either a "d" or an "h" followed by "og".

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To remove whitespace characters, such as spaces and/or tabs from a line while editing a file in the vi and Vim text editor you can use a regular expression (regexp) that incorporates \s (lowercase letter "s"), which respresents a white space character. E.g., supposing the lines below appear in a file:

450 SN/GN Tech  Edit Delete
ACE     Edit Delete
ADO             Edit Delete
AGO     Edit Delete
AGS     Edit Delete
AIM     Edit Delete
ASF         Edit Delete

I could hit the colon key and type s/\s*Edit Delete// to delete the white space after the project name that appears at the beginning of the line and the "Edit Delete" at the end of the line, so that only the project name remains. To perform the substitution for all lines, I could use 1,$ s/\s*Edit Delete//.

The 1,$ represents every line from the 1st to the last and 1,$ s/old_pattern/new_pattern/ would indicate that a substitution is to be performed on every line with new_pattern replacing old_pattern on each line. The \s represents any whitespace character and the asterisk after it indicates to look for zero or more occurrences of any whitespace character. So s/\s*Edit Delete// indicates to delete white space characters followed by the words Edit Delete.

I could also use \W, instead; \W represents any non-alphanumeric character.

Related articles:

1. gVim Portable for Windows

Reference:

1. Lesson 9: All this whitespace
   RegexOne - Learn Regular Expressions with simple, interactive exercises.

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When I attempted to edit a file, index.php, using the vi editor, I saw the following message:

E325: ATTENTION
Found a swap file by the name ".index.php.swp"
          owned by: joe   dated: Mon Feb 20 19:36:11 2017
         file name: ~joe/www/UVNC/index.php
          modified: YES
         user name: joe   host name: example.com
        process ID: 19776
While opening file "index.php"
             dated: Mon Feb 20 19:38:44 2017
      NEWER than swap file!

(1) Another program may be editing the same file.  If this is the case,
    be careful not to end up with two different instances of the same
    file when making changes.  Quit, or continue with caution.
(2) An edit session for this file crashed.
    If this is the case, use ":recover" or "vim -r index.php"
    to recover the changes (see ":help recovery").
    If you did this already, delete the swap file ".index.php.swp"
    to avoid this message.

Swap file ".index.php.swp" already exists!
[O]pen Read-Only, (E)dit anyway, (R)ecover, (D)elete it, (Q)uit, (A)bort:

I hit the q key to return to the Bash shell prompt. When I compared the time stamps on the current version of the file and the .swp file, I saw that the current version had a time stamp 2 minutes after the time stamp for the .swp file.

$ ls -al | grep 'index.php'
-rw-rw-r--. 1 joe joe   7571 Feb 20 19:38 index.php
-rw-r--r--. 1 joe joe  20480 Feb 20 19:36 .index.php.swp
$

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From the poem If— by Rudyard Kipling (1865-1936)

If you wished to delete all of the text on the line from the word "To" up until, but not including the word "And" in "And so hold on...", while in command mode, not insert mode, you could move the cursor to the "T" in "To" and then hit the d key followed by the forward slash key (/) and then type And (make sure you use the matching capitalization). The line would then appear as shown below.

Suppose, instead, you had the cursor at the word "To" as before, but wanted to delete backwards through the word "If", i.e., all the way to the beginning of the line, instead. You could then hit the d key while in command mode, then hit the question mark (?) key and type If. You would then have the text below.

For the backwards deletion, the word you type after the question mark is included in the deletion. In this case, if you wished to delete backwards to the beginning of the line, you could also have hit the d key followed by the ? key and then hit the caret (^) key, which represents the beginning of the line. Likewise, you could hit the dollar sign ($) key to delete forward to the end of the line, which it represents, or you could just hit the D key, instead of the lower-case "d" to delete from the current cursor position to the end of the line.

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If you want to replace or insert characters at the beginning of a line, the line beginning is represented by the caret character, i.e., ^ (Shift-6 on a standard computer keyboard), and line endings are represented by the dollar sign character, i.e., $.

E.g., the following quote has three occurences of the word "us". If I wanted to replace only the "us" at the end of the line with "ourselves", I could hit the colon key while not in vi's insert mode, which would give me a colon prompt and then enter s /us$/ourselves/ which would replace the occurence of "us" at the end of the lne with "ourselves".

What lies behind us and what lies before us are tiny compared to what lies within us

~ Ralph Waldo Emerson

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The wrapmargin parameter is set to an integer number of characters. When set to any nonzero number, vi will watch the lines that you type in the input modes. When you get to within the "wraprmargin" number of characters of the 80th character on the line, the next space character that you type will cause vi to enter a carriage return for you. This parameter gives vi a word wrap feature for entering text data. When set to zero, the wrap margin feature is disabled.

Source: Unix for Application Developers by William A. Parrette ©1991, page 320

If you wish to have vi display the current line and column number as you type, use :set ruler. If it is turned on you will see the current line number and column number displayed at the bottom of the vi window, e.g., 24,67 if you were on line 24 at column 67. The numbers will change as you move the cursor whether you are in input mode or not. You can turn it off with :set noruler.

Alternatively, you can also use control-G on a Mac OS X system or Ctrl-G on a Linux system or with Vim on a Microsoft Windows system, i.e., hit the control, or Ctrl, and G keys simultaneously to see the current line and column numbers. You will see something like the following displayed at the bottom of the window:

"temp.txt" [Modified] line 30 of 34 --88%-- col 32

In the above example, while editing the file temp.txt the cursor was on line 30 of the 34 lines in the file and was at column 32 when I hit control-G. Since 30 is 88% of 34, the cursor was at a point 88 percent of the way through the file. Each time you hit control-G, the status information will be displayed for the current line and column when you hit the key combination.

With vi on a Mac OS X or Linux system, you can also use !}fmt when not in input mode, to automatically wrap the text in a paragraph so that a line doesn't exceed column 80 in that paragraph from the point where you enter that command.

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In a regular expression ^ signifies the beginning of a line and $ specifies the end of a line. To have an operation apply to multiple lines at once, you can specify a range of lines, e.g. 16,25. To have the operation apply starting with the current line, you can use a period, ., to represent the current line, so .,25 would mean apply the operation to the current line and all subsequent lines up to and including line 25. Or you could specify that the operation should be applied from the current line to the end of the file by using $ to represent the last line in the file, e.g., .,$.

:% s/^/123/

The s indicates a substitute operation will follow and the forward slashes, / delineate the pattern to be replaced and the replacement pattern. In the above case, the ^ indicates the beginning of the line and the replacement pattern is 123.

When you are using / to delineate the patterns, it has a special meaning and if you want to use it in a pattern you have to "escape" its special meaning with an escape character, which is the backslash, \.

E.g. to insert </td> at the end of every line from the current line to line 25, the following regular expression could be used:

.,25 s/$/<\/td>/

Supposing that I wanted to put a <td> at the beginning of each line and a </td> at the end of each line from the current line through line 25. In that case I need to store the characters in between the beginning and end of a line. You can specify text to be stored by using parentheses, ( to mark the beginning of the area on the line to be stored and ) to mark the end. Since a period, ., represents any character and an asterisk, * represents multiple occurrences, ^(.*)$ would store all the characters on the line between the beginning and end of a line. You must also "escape" the ( and ) with the backslash escape character as well. To reuse the characters you have stored you recall them with \1 ("1" is the number one). If you had multiple occurrences of characters enclosed in parentheses, the second instance could be recalled with \2.

The line below would insert a <td> at the beginning of lines 16 through 25 and a </td> at the end of the lines.

:16,25 s/^\(.*\)$/<td>\1<\/td>

If you wished to have the editor prompt you as to whether you wanted the change made on a line, you could add a /c option at the end of the command to the editor. The command below would perform the same action as the one above on every line from line 16 to the end of the file, but would prompt you at each line as to whether the change should be made.

:.,$ s/^\(.*\)$/<td>\1<\/td>/c

You would see each line highlighted one by one as you progressed through the file with the following prompt each time.

replace with <td>\1<\/td> (y/n/a/q/l/^E/^Y)?

Answering y would result in the replacement occurring whereas answering n would result in the line remaining unchanged.

In this case, there is also a simpler means for inserting the table td tags at the beginning and end of each line as below:

s/.*/<td>&<\/td>

Again the .* represents the search pattern, which is every character on the line. The ampersand, &, also has a special meaning; it is the text that matches the search pattern, so putting it between the two tags results in all the text originally on the line remaining on the line. The / at the end of the replacement pattern can be eliminated if there is nothing following it such as a /c.

References:

1. Adding characters at the start and end of each line in a file
   May 2, 2012
   Stack Overflow
2. Search and replace
   Vim Tips Wiki

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References:

1. reformatting
   vim tips and tricks

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Original lines

Gold, Silver, Bronze

Desired lines

Gold Silver Bronze

You can use the following command in Vi to replace all commas with the newline character starting from the first line in the file to the last (represented by $):

1,$ s/,/^M/g

As noted above, you need to hit Ctrl-V Enter to put the ^M in the command.

References:

1. How to represent a new line character in a regex in VI?
   By: mbrooks
   Date: December 30, 2006
   Tek-Tips

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