Found a neat trick for doing recursive one-liners


#1

This is probably something everyone in here already knows about, but I
thought it was cool enough that I wanted to post about it.

If you want to create a one liner to say search all the *.txt files
in and under the current directory for text matching “Hello”, you can do
this

find -name ‘*.txt’ -exec ruby -ne ‘print if /Hello/’ ‘{}’ ‘;’

I know you can do this in pure ruby in like 3 lines if you use the Find
module, but I really wanted to do it with a one liner. Earlier I tried
something like this

ruby -ne ‘print if /Hello/’ find -name '*.txt'

unfortunately that version would fail if there were any spaces in the
filenames.


#2

–Cool to use throw ruby into the -exec but I would just use grep in
that scenerio.


#3

Or you can use the tools designed for finding stuff :slight_smile:

find . -name “*.txt” | xargs grep Hello

That version will work for all files. You can play with find to match
any file you want.

Pat


#4

Hi,

At Tue, 27 Dec 2005 12:57:53 +0900,
Gary W. wrote in [ruby-talk:172611]:

I know you can do this in pure ruby in like 3 lines if you use the Find
module, but I really wanted to do it with a one liner. Earlier I tried
something like this

ruby -ne ‘print if /Hello/’ find -name '*.txt'

unfortunately that version would fail if there were any spaces in the
filenames.

ruby -ne ‘BEGIN{ARGV.replace(Dir[ARGV.join("\0")])}; print if /Hello/’
‘**/*.txt’


#5

I apologize for using a brain dead example. I was more excited about
the
prospect of hitting all files under the current directory recursively,
not
the actual processing I used in my examples. Thanks for the pointer to
xargs. I didn’t know about that one, I’ll have to take a closer look at
it’s man page.


#6

Ara, I always love your examples! :slight_smile: Please keep contributing to the
community!!

BTW, I have the process management class working like a champ… I’ll
share the code with you later!


#7

On Tue, 27 Dec 2005, Gary W. wrote:

module, but I really wanted to do it with a one liner. Earlier I tried
something like this

ruby -ne ‘print if /Hello/’ find -name '*.txt'

ruby -e’ puts Dir["/"].select{|e| e =~ /a.rb/} ’

-a


#8

I know Im a n00b, but I think more than anything, its good to see you so
excited about Ruby. Learning new things really is fun in Ruby.

On Mon, 26 Dec 2005 20:22:52 -0800, Gary W. removed_email_address@domain.invalid


#9

Pat M. wrote:

Or you can use the tools designed for finding stuff :slight_smile:

find . -name “*.txt” | xargs grep Hello

That version will work for all files. You can play with find to match
any file you want.

Assuming you are on a machine with find, xargs, and grep, as opposed to
just Ruby.

I like the idea of assembling command line utils that will work on any
platform where Ruby is installed (e.g., all the machines in my house).

I also like the idea of reinventing the wheel in Ruby because sometimes
you get a better wheel. Or at least one that is more hackable.

James

http://www.ruby-doc.org - Ruby Help & Documentation
http://www.artima.com/rubycs/ - Ruby Code & Style: Writers wanted
http://www.rubystuff.com - The Ruby Store for Ruby Stuff
http://www.jamesbritt.com - Playing with Better Toys
http://www.30secondrule.com - Building Better Tools


#10

Hi –

On Tue, 27 Dec 2005, removed_email_address@domain.invalid wrote:

I know you can do this in pure ruby in like 3 lines if you use the Find
module, but I really wanted to do it with a one liner. Earlier I tried
something like this

ruby -ne ‘print if /Hello/’ find -name '*.txt'

ruby -e’ puts Dir["/"].select{|e| e =~ /a.rb/} ’

We’ve strayed a little from the original thing, but along those lines
you could also do:

ruby -e ‘puts Dir["/"].grep(/a.rb/)’

(just guessing about the . part :slight_smile:

or maybe even:

ruby -e 'puts Dir["**/a.rb/"]

David


David A. Black
removed_email_address@domain.invalid

“Ruby for Rails”, from Manning Publications, coming April 2006!


#11

Ara,

On Tue, 2005-12-27 at 13:22 +0900, removed_email_address@domain.invalid wrote:

I know you can do this in pure ruby in like 3 lines if you use the Find
module, but I really wanted to do it with a one liner. Earlier I tried
something like this

ruby -ne ‘print if /Hello/’ find -name '*.txt'

ruby -e’ puts Dir["/"].select{|e| e =~ /a.rb/} ’

That doesn’t seem to do anything . .

Phil.

Philip R.

Pricom Pty Limited (ACN 003 252 275 ABN 91 003 252 275)
GPO Box 3411
Sydney NSW 2001
Australia
Mobile: +61:(0)411-185-652
Fax: +61:(0)2-8221-9599
E-mail: removed_email_address@domain.invalid


#12

In article
removed_email_address@domain.invalid,
Pat M. removed_email_address@domain.invalid wrote:

Or you can use the tools designed for finding stuff :slight_smile:

find . -name “*.txt” | xargs grep Hello

That version will work for all files.

Not quite. For better (maximum?) robustness, pass '-print0' to find and '-0' to xargs. That will handle filenames with spaces and/or quotes correctly. (If your filenames have bytes with binary value zero in them, you still will be out of luck)

Reinder


#13

On Tue, 27 Dec 2005, Pat M. wrote:

Or you can use the tools designed for finding stuff :slight_smile:

find . -name “*.txt” | xargs grep Hello

That version will work for all files. You can play with find to match
any file you want.

find . -regex ‘.*.txt’ -print0 | xargs -0 -n1000 grep Hello

-print0 and -0 to avoid trouble with spaces and other metagubbins.
-n1000 for a bit of a speedup
-regex to show you can :wink:


#14

I really prefer the simple variant…
ruby -e ‘puts Dir["**/a*.{rb}"]’

finds all .rb that start with ‘a’, recursive of course :slight_smile:

Am Dienstag, 27. Dezember 2005 11:36 schrieb removed_email_address@domain.invalid:


#15

Pat M. wrote:

Or you can use the tools designed for finding stuff :slight_smile:

find . -name “*.txt” | xargs grep Hello

That version will work for all files. You can play with find to match
any file you want.

Pat

et@adel:/tmp/rb$ touch ‘foo bar.txt’
et@adel:/tmp/rb$ find . -name “.txt"
…/foo bar.txt
et@adel:/tmp/rb$ find . -name "
.txt” | xargs grep Hello
grep: ./foo: No such file or directory
grep: bar.txt: No such file or directory
et@adel:/tmp/rb$ find . -name “*.txt” -print0 | xargs -0 grep Hello
et@adel:/tmp/rb$

Watch out if you are using xargs. It can get pretty nasty, especially if
there is not grep at work, but rm or alike.

Shooting yourself in the foot 101:
$ touch “foo … bar -rf moo.o”
$ find . -name ‘*.o’ | xargs rm
BAM

If you are using find and xargs, always use -print0 and -0,
respectively.

Regards,
Stefan


#16

On Wed, 28 Dec 2005, Christian N. wrote:

Reinder V. removed_email_address@domain.invalid writes:

Not quite. For better (maximum?) robustness, pass '-print0' to find and '-0' to xargs. That will handle filenames with spaces and/or quotes correctly. (If your filenames have bytes with binary value zero in them, you still will be out of luck)

Know an OS where that is allowed?

NT 4 kernel mode API is quite happy with \0 in filenames. But it
really
confuses the Win32 layer! Haven’t played with later versions…


#17

Reinder V. removed_email_address@domain.invalid writes:

Not quite. For better (maximum?) robustness, pass '-print0' to find and '-0' to xargs. That will handle filenames with spaces and/or quotes correctly. (If your filenames have bytes with binary value zero in them, you still will be out of luck)

Know an OS where that is allowed?


#18

On Tue, 27 Dec 2005, Philip R. wrote:

ruby -e’ puts Dir["/"].select{|e| e =~ /a.rb/} ’

That doesn’t seem to do anything . .

then you probably don’t have any files named ‘a.rb’ under the current
directory - i seem to have several hundred :wink:

cheers.

-a


#19

On Wed, 28 Dec 2005 removed_email_address@domain.invalid wrote:

then you probably don’t have any files named ‘a.rb’ under the current
directory - i seem to have several hundred :wink:

Or abrb, or acrb, or airbag, or… :slight_smile:

indeed. or diectories. that’s the nice thing about using select:

ruby -e’ puts Dir["/"].select{|e| test ?f, e and e =~ /^a.rb$/}

-a


#20

Hi –

On Wed, 28 Dec 2005, removed_email_address@domain.invalid wrote:

On Tue, 27 Dec 2005, Philip R. wrote:

ruby -e’ puts Dir["/"].select{|e| e =~ /a.rb/} ’

That doesn’t seem to do anything . .

then you probably don’t have any files named ‘a.rb’ under the current
directory - i seem to have several hundred :wink:

Or abrb, or acrb, or airbag, or… :slight_smile:

David


David A. Black
removed_email_address@domain.invalid

“Ruby for Rails”, from Manning Publications, coming April 2006!