Tip #227: Power of :g

tip karma

Rating 408/159, Viewed by 12039

created:		March 24, 2002 3:15		complexity:		intermediate
author:		Arun Easi		as of Vim:		5.7

:g is something very old and which is very powerful. I just wanted to illustrate the use of it with some examples. Hope, it will be useful for someone. Brief explanation for ":g" ------------------------- Syntax is: :[range]:g/<pattern>/[cmd] You can think the working as, for the range (default whole file), execute the colon command(ex) "cmd" for the lines matching <pattern>. Also, for all lines that matched the pattern, "." is set to that particular line (for certain commands if line is not specified "." (current line) is assumed). Some examples ------------- Display context (5 lines) for all occurences of a pattern :g/<pattern>/z#.5 :g/<pattern>/z#.5|echo "==========" << same as first, but with some beautification >> Delete all lines matching a pattern :g/<pattern>/d Delete all blank lines (just an example for above) :g/^\s*$/d Double space the file :g/^/pu =\"\n\" :g/^/pu _ << the above one also works >> Copy all lines matching a pattern to end of file :g/<pattern>/t$ Yank all lines matching a pattern to register 'a' 0"ay0:g/<pattern>/y A Increment the number items from current line to end-of-document by one :.,$g/^\d/exe "normal! \<c-a>" Comment (C) lines containing "DEBUG" statements g/^\s*DEBUG/exe "norm! I/* \<Esc>A */\<Esc>" A Reverse lookup for records (eg: An address book, with Name on start-of-line and fields after a space) :g/<patern>?^\w?p "if only name is interested :g/<patern>/ka|?^\w?p|'ap "if name and the lookup-line is interested :g/<patern>/?^\w?|+,/^[^ ]/-1p "if entire record is interested Reverse a file (just to show the power of 'g') :g/^/m0 Foot note 1: use :v to negate the search pattern Foot note 2: Some explanation of commonly used commands with :g :2,8co15 => Copy lines 2 through 8 after line 15 :4,15t$ => Copy linesa 4 through 15 towards end of document (t == co) :-t$ => Copy previous line to end of document :m0 => Move current line to the top of the document :.,+3m$-1 => Move current line through cur-line+3 to the last but one line of the document Foot note 3: Commands used with :g are ex commands, so a help search should be, :help :<help-topic> eg. :help :k

<<Edit file under cursor after a horizontal split | Deleting nested reply threads in emails >>

Additional Notes

[email protected], March 28, 2002 7:10

Thanx Karma for extending my g// knowledge Here's a very useful g// for day to day use :'a,'bg/pattern/s/pattern2/string3/gi zzapper

Hal Atherton, April 23, 2002 10:12

g WITH CONFIRM c Here's something very curious: :%s/foo/bar/gc is of course a substitution effective for the entire file with confirm on each occurrence of "foo" with the option of quitting at any point. However, using something similar, :g/foo/s//bar/gc using the global g to effect the entire file -- does NOT allow quitting at any point (even with the use of <ESC>). If there are hundreds of "foo" -- it's an important fine point... Invite further comments...

Arun Easi, April 23, 2002 23:33

g/foo/s//bar/gc => run the command s//bar/gc for each of the line matching foo. It is like running multiple "s//" commands (Hence you have to press q for each of the invocation). The g in "s///gc" does not imply entire file, it just implies all occurence on a line (or else, it would have substituted only the first)

[email protected], May 30, 2002 9:04

Here is one that deletes every other line (adjusting double spaced files): :g/.*/norm jdd

pagaltzis()gmx_de, August 6, 2002 15:12

This can be done much simpler: :%norm jdd

[email protected], February 10, 2003 4:49

Another cool g feature is to count the number of lines matching /regexp/ let x=0 | g/regexp/let x=x+1 echo x Great, if you are editing data files. Regards Mike

[email protected], March 27, 2003 2:14

Reverse all the lines in a file: :g/^/m0 I have found that useful . . . honest! PK

[email protected], September 3, 2003 5:06

Can I do something like this using ":g" (or anything else) I have a file which contains following kind of lines abc123=1,2,3 bcd123=100,200,300 abcb123=1,3,4 I want to convert this to following abc123=1,abc,2,abc,3,abc bcd123=100,bcd,200,bcd,300,bcd abcb123=1,abcb,3,abcb,4,abcb Basically I want to replace each comma in a line with first few letters, which are coming before 123, of that line surrounded by 2 commas.

Anonymous, September 3, 2003 12:45

To answer kkgahlot's question: global // execute "s/\$[=,][^,]*\$/\\1, " . matchstr (getline ("."), "^.\\{-}\$123\$\\@=") . "/g" To make the whole thing a little more transparent some explanations (from the inside out): We want to execute on each line a command like s/$[=,][^,]*$/\1, abc/g for each line, but abc gets changed on each line. The function matchstr (getline ("."), "^.\\{-}\$123\$\\@=") returns the string that matches the pattern /^.\{-}$123)\@=/ on the current line. In the given examples this is the text preceding 123= at the beginning of the line. Depending on the actual requierements, a simpler expression like /^[a-z]*/ could work too. The command execute "s/\\([=,][^,]*\$/\\1, " . matchstr (getline ("."), "^.\\{-}\$123\$\\@=") . "/g" assembles the desired substitute command for the current line by joining some static text with the return value of the matchstr function and then executes it. As execute works only on the current line, the command global // execute ... applies it to all line. If only certain lines should be proecessed replace // with some other pattern.

[email protected], November 21, 2003 10:39

Reverting lines in a file can also be done via :%!tac instead of tac, you can also use sort, xxd, xxd -r, cut, your-own-filter

Anonymous, March 29, 2004 7:18

too bad :g does not have a /c parameter for confirmed execution of ex commands. Something like the /c used in :<range>s/<PAT>/<REPL>/c for replacing only confirmed pattern locations. or does it ??

[email protected], April 14, 2004 10:06

I just want to add that the :g command in vi/ed is the basis for the name for the Unix grep command, i.e. Global Regular Expression Print. The "Print" part described the default behaviour of :g when no command was given. Obviously this behaviour was more useful when using ed.

[email protected], August 16, 2004 23:55

Thank you for the tip




	If you have questions or remarks about this site, visit the vimonline development pages. Please use this site responsibly. Questions about Vim should go to [email protected] after searching the archive. Help Bram help Uganda.