Emacs equivalent of the ":g" command in vi

Emacs equivalent of the ":g" command in vi

[C K Kashyap]

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Hi,
Could someone please tell me how I could go about something like this -
I need to perform a certain action (such as delete the line) on each line of
a buffer if the line matches a regular expression. In vim, we can use the :g
command for this.
Regards,
Kashyap

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Re: Emacs equivalent of the ":g" command in vi

[Peter Dyballa]

Am 22.07.2011 um 10:42 schrieb C K Kashyap:

> I need to perform a certain action (such as delete the line) on each line of
> a buffer if the line matches a regular expression. In vim, we can use the :g
> command for this.

I don't know that :g in vim that exactly, I prefer to use ``.´´ from time to time.

GNU Emacs allows to use three commands:

	repeat
	repeat-complex-command
	repeat-matching-complex-command

See which one can be used! (Deleting a single line is simple: C-k, deleting a bunch of lines is also quite simple: C-u <number> C-k – which could be as simple as in vi/vim.)

--
Greetings

  Pete

There's no place like ~
			– (UNIX Guru)

Re: Emacs equivalent of the ":g" command in vi

[Thierry Volpiatto]

Peter Dyballa <Peter_Dyballa@Web.DE> writes:

> Am 22.07.2011 um 10:42 schrieb C K Kashyap:
>
>> I need to perform a certain action (such as delete the line) on each line of
>> a buffer if the line matches a regular expression. In vim, we can use the :g
>> command for this.
>
> I don't know that :g in vim that exactly, I prefer to use ``.´´ from time to time.
>
> GNU Emacs allows to use three commands:
>
> 	repeat
> 	repeat-complex-command
> 	repeat-matching-complex-command
>
> See which one can be used! (Deleting a single line is simple: C-k,
> deleting a bunch of lines is also quite simple: C-u <number> C-k –
> which could be as simple as in vi/vim.)
I think he want to delete lines matching a regexp, so C-k is not what he
wants here.

`query-replace-regexp' can be used with a regexp like this:

^.*\(your_regexp\).*$

and you replace with nothing (empty prompt).

-- 
A+ Thierry
Get my Gnupg key:
gpg --keyserver pgp.mit.edu --recv-keys 59F29997 

Re: Emacs equivalent of the ":g" command in vi

[C K Kashyap]

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>
> > which could be as simple as in vi/vim.)
> I think he want to delete lines matching a regexp, so C-k is not what he
> wants here.
>
> `query-replace-regexp' can be used with a regexp like this:
>
> ^.*\(your_regexp\).*$
>
> and you replace with nothing (empty prompt).
>
> --
>

replace-regexp is indeed closer to what I am looking for. However, I'd like
the result to not leave blank lines.

Regards,
Kashyap

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Re: Emacs equivalent of the ":g" command in vi

[Peter Dyballa]

Am 22.07.2011 um 12:02 schrieb C K Kashyap:

> I'd like the result to not leave blank lines.

Then modify the regexp to:

	^.*\(your_regexp\).*^J

The final ^J (LINEFEED character) can be input as C-q C-j or as C-o.

--
Greetings

  Pete

Globalisation – communism from above.

Re: Emacs equivalent of the ":g" command in vi

[C K Kashyap]

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On Fri, Jul 22, 2011 at 3:42 PM, Peter Dyballa <Peter_Dyballa@web.de> wrote:

>
> Am 22.07.2011 um 12:02 schrieb C K Kashyap:
>
> > I'd like the result to not leave blank lines.
>
> Then modify the regexp to:
>
>        ^.*\(your_regexp\).*^J
>
> The final ^J (LINEFEED character) can be input as C-q C-j or as C-o.
>
> --
> Greetings
>
>  Pete
>
> Globalisation – communism from above.
>
>
Thanks Pete ... this works for me.
Kashyap

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Re: Emacs equivalent of the ":g" command in vi

[Thien-Thi Nguyen]

() C K Kashyap <ckkashyap@gmail.com>
() Fri, 22 Jul 2011 15:32:10 +0530

   However, I'd like the
   result to not leave blank lines.

Try ‘M-x flush-lines’.
Use ‘C-h f flush-lines RET’ first to avoid surprises.

Re: Emacs equivalent of the ":g" command in vi

[C K Kashyap]

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>
> () C K Kashyap <ckkashyap@gmail.com>
> () Fri, 22 Jul 2011 15:32:10 +0530
>
>   However, I'd like the
>   result to not leave blank lines.
>
> Try ‘M-x flush-lines’.
> Use ‘C-h f flush-lines RET’ first to avoid surprises.
>

this does exactly what I was looking for.
Kashyap

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Re: Emacs equivalent of the ":g" command in vi

[Deniz Dogan]

On 2011-07-22 12:02, C K Kashyap wrote:
>      > which could be as simple as in vi/vim.)
>     I think he want to delete lines matching a regexp, so C-k is not what he
>     wants here.
>
>     `query-replace-regexp' can be used with a regexp like this:
>
>     ^.*\(your_regexp\).*$
>
>     and you replace with nothing (empty prompt).
>
>     --
>
>
> replace-regexp is indeed closer to what I am looking for. However, I'd
> like the result to not leave blank lines.
>
> Regards,
> Kashyap

First, either move to the start of where you want to search OR make an 
active region (select) the parts where you want it to take effect.  M-< 
goes to the beginning of the buffer and C-x h marks the whole buffer, FYI.

Now, M-x delete-matching-lines RET your_regexp RET

Deniz

Re: Emacs equivalent of the ":g" command in vi

[Deniz Dogan]

On 2011-07-22 12:45, Deniz Dogan wrote:
> On 2011-07-22 12:02, C K Kashyap wrote:
>> > which could be as simple as in vi/vim.)
>> I think he want to delete lines matching a regexp, so C-k is not what he
>> wants here.
>>
>> `query-replace-regexp' can be used with a regexp like this:
>>
>> ^.*\(your_regexp\).*$
>>
>> and you replace with nothing (empty prompt).
>>
>> --
>>
>>
>> replace-regexp is indeed closer to what I am looking for. However, I'd
>> like the result to not leave blank lines.
>>
>> Regards,
>> Kashyap
>
> First, either move to the start of where you want to search OR make an
> active region (select) the parts where you want it to take effect. M-<
> goes to the beginning of the buffer and C-x h marks the whole buffer, FYI.
>
> Now, M-x delete-matching-lines RET your_regexp RET
>

You may also want to know about:

Global Bindings Starting With M-s:
key             binding
---             -------

M-s h           Prefix Command
M-s o           occur
M-s w           isearch-forward-word

M-s h f         hi-lock-find-patterns
M-s h l         highlight-lines-matching-regexp
M-s h p         highlight-phrase
M-s h r         highlight-regexp
M-s h u         unhighlight-regexp
M-s h w         hi-lock-write-interactive-patterns

As you can see, e.g. M-s h r can be very useful at times.

Deniz

Re: Emacs equivalent of the ":g" command in vi

[Eric Abrahamsen]

On Fri, Jul 22 2011, C K Kashyap wrote:

>     > which could be as simple as in vi/vim.)
>     I think he want to delete lines matching a regexp, so C-k is not
>     what he
>     wants here.
>    
>     `query-replace-regexp' can be used with a regexp like this:
>    
>     ^.*\(your_regexp\).*$
>    
>     and you replace with nothing (empty prompt).
>    
>     --
>
>
> replace-regexp is indeed closer to what I am looking for. However,
> I'd like the result to not leave blank lines.
>
> Regards,
> Kashyap 

Isn't this what flush-lines and keep-lines are for?

Re: Emacs equivalent of the ":g" command in vi

[MBR]

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On 7/22/2011 4:42 AM, C K Kashyap wrote:
> Hi,
> Could someone please tell me how I could go about something like this -
> I need to perform a certain action (such as delete the line) on each 
> line of a buffer if the line matches a regular expression. In vim, we 
> can use the :g command for this.
> Regards,
> Kashyap

I looked for the same thing ages ago when I switched from vi to emacs.  
Eventually I figured out that:

    :g/regular expression/operation

reflects an 'ed' mindset, and that an Emacs macro with a repeat count is 
actually far more powerful .  (In case you're wondering what 'ed' is, it 
was the original, line-oriented, Unix editor.  'vi' was Bill Joy's 
visual mode version of 'ex', which was his enhanced version of 'ed'.)

An Emacs macro is a series of emacs commands that you can replay.  You 
use C-( and C-) as follows to create a macro:

    C-(
    type any commands you want Emacs to remember
    C-)

Then, whenever you type C-x e, Emacs will replay the commands.

At this point, you're probably wondering how this can substitute for 
vi's g//.  Simple.  Just start your macro off with a regular expression 
search, do whatever you want, and then replay it multiple times with:

    C-u /count/ C-x e

Specify a large enough repeat count, and you can make your macro apply 
to the whole file.

For example, to delete each line of a buffer if the line matches a 
regular expression, you'd define the macro with:

    C-(            ;; Begin recording macro
    C-M-s regexp    ;; Search for regular expression
    C-a            ;; Go to beginning of line
    C-k             ;; Kill one line by typing C-k twice
    C-k            ;;
    C-)            ;; End recording macro

Then you'd execute the macro with:

    C-u 10000 C-x e

Of course, there's an easier way to delete lines that match a regular 
expression:

    M-x delete-matching-lines

But you described the general problem as needing to perform a certain 
action on each line of a buffer if the line matches a regular 
expression.  And the approach of defining a macro to do what you want 
and then executing it with a large repeat count gives you a general 
purpose mechanism to do arbitrary operations rather than just delete the 
line.

For example, if I have a file of lines of the format:

    zip,street address,city,state,phone,name

That I wanted to rearrange to:

    name,phone,street address,city,state,zip

I could run:

    M-x replace-regexp
    ^\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\)$
    \6,\5,\2,\3,\4,\1

which is the equivalent of vi's:

    :g/^\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\)$/s//\6,\5,\2,\3,\4,\1/g

But making sure you've got that regular expression right can be tricky.  
It can be much easier to just do it with emacs commands applied to a 
single line.  Although the following is difficult to read, I think if 
you try it out you'll find it pretty straightforward.  First fill an 
emacs buffer with lots of lines of the form:

    name,phone,street address,city,state,zip

Then type these emacs keystrokes (omitting the comments):

    ;; Begin recording macro
    C-(
    ;; Narrow the buffer to the current line:
    C-SPC C-n C-x n n M-<
    ;; Move the part after the fifth ","
    ;; to the beginning of the line
    C-s , C-s C-s C-s C-s C-b C-k C-a C-y , C-a C-d
    ;; Move the part that's now after the fifth ","
    ;; to the second comma-delimited position
    C-s , 4*C-s C-b C-k C-a M-f C-y
    ;; Move the third comma-delimited part to the end
    M-d C-e C-y
    ;; Move forward over the newline to the next line
    C-f
    ;; Widen so you can see the whole buffer
    C-x n w
    ;; End recording macro
    C-)

Replay it 10,000 times with:

    C-u 10000 C-x e

It will stop as soon as it runs out of matching lines.

The point is that the operations you can repeat this way are limited 
only by your imagination.

There's a variant of this that I use frequently.  I often find that a 
non-emacs application wants me to type lots of information into 
individual fields of an input screen.  It's a pain to have to type all 
that data, especially when I have that data in a text file.  In emacs I 
can organize the data into the same order as the input fields in the 
application, putting each field's data on a separate line of the emacs 
buffer.  Then I do the following in emacs:

    ;; Begin recording macro
    C-(
    ;; Mark region from beginning to end of line
    C-aC-SPCC-e
    ;; Copy region so it can be pasted into another application
    C-w
    ;; Move forward over the newline to the next line
    C-f
    ;; End recording macro
    C-)

Once I've defined that macro, I can repeatedly type:

    ;; This is not an Emacs command.  It tells the window manager
    ;; to give keyboard focus to the other application.
    ALT-TAB
    ;; Paste into the input field
    C-v
    ;; Move focus to the next input field
    TAB
    ;; Give keyboard focus to Emacs.
    ALT-TAB
    ;; Repeat the macro, which copies the next line.
    C-x e

At that point, I repeatedly type:

    C-x e ALT-TAB C-v TAB ALT-TAB

While it's not fully automated, If I've got lots of data that has to be 
entered through a GUI interface, it makes things go a whole lot faster.

If you should want to save a macro you've created this way so you can 
use it in future Emacs sessions:

    Open your .emacs file: C-x C-f ~/.emacs
    Give it a name by with:M-x name-last-kbd-macro
    Insert it into your .emacs with: M-x insert-kbd-macro
    Save your .emacs file: C-x C-s

                Mark Rosenthal
                mbr@arlsoft.com <mailto:mbr@arlsoft.com>

P.S. - Interesting side-note.  Did you know that the ed command:

     g/regular expression/operation

is where the name "grep" came from?  In ed and ex, the "g" means do a 
global search for the immediately following regular expression, and 
apply the operation to every matching line.  One such operation is "p" 
meaning "print".  Using "re" as shorthand for "regular expression", the 
ed command to print every line that matches a particular regular 
expression is:

                 g/re/p



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Re: Emacs equivalent of the ":g" command in vi

[Andreas Röhler]

Am 22.07.2011 22:27, schrieb MBR:
> On 7/22/2011 4:42 AM, C K Kashyap wrote:
>> Hi,
>> Could someone please tell me how I could go about something like this -
>> I need to perform a certain action (such as delete the line) on each
>> line of a buffer if the line matches a regular expression. In vim, we
>> can use the :g command for this.
>> Regards,
>> Kashyap
>
> I looked for the same thing ages ago when I switched from vi to emacs.
> Eventually I figured out that:
>
> :g/regular expression/operation
>
> reflects an 'ed' mindset, and that an Emacs macro with a repeat count is
> actually far more powerful . (In case you're wondering what 'ed' is, it
> was the original, line-oriented, Unix editor. 'vi' was Bill Joy's visual
> mode version of 'ex', which was his enhanced version of 'ed'.)
>
> An Emacs macro is a series of emacs commands that you can replay. You
> use C-( and C-) as follows to create a macro:
>
> C-(
> type any commands you want Emacs to remember
> C-)
>
> Then, whenever you type C-x e, Emacs will replay the commands.
>
> At this point, you're probably wondering how this can substitute for
> vi's g//. Simple. Just start your macro off with a regular expression
> search, do whatever you want, and then replay it multiple times with:
>
> C-u /count/ C-x e
>
> Specify a large enough repeat count, and you can make your macro apply
> to the whole file.
>
> For example, to delete each line of a buffer if the line matches a
> regular expression, you'd define the macro with:
>
> C-( ;; Begin recording macro
> C-M-s regexp ;; Search for regular expression
> C-a ;; Go to beginning of line
> C-k ;; Kill one line by typing C-k twice
> C-k ;;
> C-) ;; End recording macro
>
> Then you'd execute the macro with:
>
> C-u 10000 C-x e
>
> Of course, there's an easier way to delete lines that match a regular
> expression:
>
> M-x delete-matching-lines
>
> But you described the general problem as needing to perform a certain
> action on each line of a buffer if the line matches a regular
> expression. And the approach of defining a macro to do what you want and
> then executing it with a large repeat count gives you a general purpose
> mechanism to do arbitrary operations rather than just delete the line.
>
> For example, if I have a file of lines of the format:
>
> zip,street address,city,state,phone,name
>
> That I wanted to rearrange to:
>
> name,phone,street address,city,state,zip
>
> I could run:
>
> M-x replace-regexp
> ^\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\)$
> \6,\5,\2,\3,\4,\1
>
> which is the equivalent of vi's:
>
> :g/^\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\),\([^,]*\)$/s//\6,\5,\2,\3,\4,\1/g
>
>
> But making sure you've got that regular expression right can be tricky.
> It can be much easier to just do it with emacs commands applied to a
> single line. Although the following is difficult to read, I think if you
> try it out you'll find it pretty straightforward. First fill an emacs
> buffer with lots of lines of the form:
>
> name,phone,street address,city,state,zip
>
> Then type these emacs keystrokes (omitting the comments):
>
> ;; Begin recording macro
> C-(
> ;; Narrow the buffer to the current line:
> C-SPC C-n C-x n n M-<
> ;; Move the part after the fifth ","
> ;; to the beginning of the line
> C-s , C-s C-s C-s C-s C-b C-k C-a C-y , C-a C-d
> ;; Move the part that's now after the fifth ","
> ;; to the second comma-delimited position
> C-s , 4*C-s C-b C-k C-a M-f C-y
> ;; Move the third comma-delimited part to the end
> M-d C-e C-y
> ;; Move forward over the newline to the next line
> C-f
> ;; Widen so you can see the whole buffer
> C-x n w
> ;; End recording macro
> C-)
>
> Replay it 10,000 times with:
>
> C-u 10000 C-x e
>
> It will stop as soon as it runs out of matching lines.
>
> The point is that the operations you can repeat this way are limited
> only by your imagination.
>
> There's a variant of this that I use frequently. I often find that a
> non-emacs application wants me to type lots of information into
> individual fields of an input screen. It's a pain to have to type all
> that data, especially when I have that data in a text file. In emacs I
> can organize the data into the same order as the input fields in the
> application, putting each field's data on a separate line of the emacs
> buffer. Then I do the following in emacs:
>
> ;; Begin recording macro
> C-(
> ;; Mark region from beginning to end of line
> C-aC-SPCC-e
> ;; Copy region so it can be pasted into another application
> C-w
> ;; Move forward over the newline to the next line
> C-f
> ;; End recording macro
> C-)
>
> Once I've defined that macro, I can repeatedly type:
>
> ;; This is not an Emacs command. It tells the window manager
> ;; to give keyboard focus to the other application.
> ALT-TAB
> ;; Paste into the input field
> C-v
> ;; Move focus to the next input field
> TAB
> ;; Give keyboard focus to Emacs.
> ALT-TAB
> ;; Repeat the macro, which copies the next line.
> C-x e
>
> At that point, I repeatedly type:
>
> C-x e ALT-TAB C-v TAB ALT-TAB
>
> While it's not fully automated, If I've got lots of data that has to be
> entered through a GUI interface, it makes things go a whole lot faster.
>
> If you should want to save a macro you've created this way so you can
> use it in future Emacs sessions:
>
> Open your .emacs file: C-x C-f ~/.emacs
> Give it a name by with:M-x name-last-kbd-macro
> Insert it into your .emacs with: M-x insert-kbd-macro
> Save your .emacs file: C-x C-s
>
> Mark Rosenthal
> mbr@arlsoft.com <mailto:mbr@arlsoft.com>
>
> P.S. - Interesting side-note. Did you know that the ed command:
>
> g/regular expression/operation
>
> is where the name "grep" came from? In ed and ex, the "g" means do a
> global search for the immediately following regular expression, and
> apply the operation to every matching line. One such operation is "p"
> meaning "print". Using "re" as shorthand for "regular expression", the
> ed command to print every line that matches a particular regular
> expression is:
>
> g/re/p
>
>
>

Hi,

from my feeling: finally much easier then fighting which recorded 
keyboard-macros is writing it's own little functions.

Running them under edebug then and a breakpoint set allows neatly control

Keyboard macros are good for really limited and easy repeats.

Andreas

Re: Emacs equivalent of the ":g" command in vi

[MBR]

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Personally, I don't find I'm "fighting" with macros.  You can get an 
astounding amount done with macros without having to do the mental 
context switch to coding mode.  And if I'm already in coding mode, I 
find putting the real application I was working on (in Java or C or PHP 
or JavaScript or whatever) on short-term hold and switching context to 
writing Elisp code for editing the application code, leaves me 
struggling to remember what I was trying to accomplish with my changes 
to the application code when I finally finish writing the Elisp code and 
need to pop that context off my mental stack and return to thinking 
about the application code.

But other people's mental processes may well be different.  To each his 
own.  Or, as they say, YMMV.

    Mark


On 7/22/2011 4:37 PM, Andreas Röhler wrote:
> Hi,
>
> from my feeling: finally much easier then fighting which recorded 
> keyboard-macros is writing it's own little functions.
>
> Running them under edebug then and a breakpoint set allows neatly control
>
> Keyboard macros are good for really limited and easy repeats.
>
> Andreas
>

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Re: Emacs equivalent of the ":g" command in vi

[Andreas Röhler]

Am 22.07.2011 22:51, schrieb MBR:
> Personally, I don't find I'm "fighting" with macros. You can get an
> astounding amount done with macros without having to do the mental
> context switch to coding mode. And if I'm already in coding mode, I find
> putting the real application I was working on (in Java or C or PHP or
> JavaScript or whatever) on short-term hold and switching context to
> writing Elisp code for editing the application code, leaves me
> struggling to remember what I was trying to accomplish with my changes
> to the application code when I finally finish writing the Elisp code and
> need to pop that context off my mental stack and return to thinking
> about the application code.
>
> But other people's mental processes may well be different. To each his
> own. Or, as they say, YMMV.
>
> Mark

Sure. If you like, it might be of interest for others too comparing a 
real example.

If you may provide a piece of code and a kbd-macro dealing with it, 
let's see how a function might come up with.

BTW as for functions you will have templates. So quite often creating a 
new function isn't much more finally than specifying a regexp.


Andreas

Re: Emacs equivalent of the ":g" command in vi

[Ken Goldman]

On 7/22/2011 4:51 PM, MBR wrote:
> Personally, I don't find I'm "fighting" with macros. You can get an
> astounding amount done with macros without having to do the mental
> context switch to coding mode.

I agree with this.  I use keyboard macros all the time for complicated 
editing functions that I only have to do once.  Define it, then M-x big 
number.

True, they can be slow, but they're still faster than trying to code up 
the 'right way' to do it.

Re: Emacs equivalent of the ":g" command in vi

[C K Kashyap]

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>
> Save your .emacs file: C-x C-s
>
>   Mark Rosenthal
> mbr@arlsoft.com
>
>   P.S. - Interesting side-note.  Did you know that the ed command:
>
>     g/regular expression/operation
>
> is where the name "grep" came from?  In ed and ex, the "g" means do a
> global search for the immediately following regular expression, and apply
> the operation to every matching line.  One such operation is "p" meaning
> "print".  Using "re" as shorthand for "regular expression", the ed command
> to print every line that matches a particular regular expression is:
>
>                 g/re/p
>
>
>
Thank you very much Mark for the detailed explanation and the interesting
side note :) I am inclined to the macro approach since the possibilities are
endless.

Regards,
Kashyap

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Re: Emacs equivalent of the ":g" command in vi

[suvayu ali]

On Sat, Jul 23, 2011 at 5:02 AM, C K Kashyap <ckkashyap@gmail.com> wrote:
> I am inclined to the macro approach since the possibilities are endless.

Keyboard macros are great and all, but I wouldn't recommend repeating
it more than a few hundred times. They are slow and sensitive to
external conditions. If your use case requires a repetition of a
thousand or more times, I would recommend `eval' (M-:) or an elisp
function. I have gone down the keyboard macro route once and regretted
it with a large file (~10,000 lines long).

-- 
Suvayu

Open source is the future. It sets us free.