[gentoo-user] [OT] Use of sed

[gentoo-user] [OT] Use of sed

[Peter Humphrey]

Hello list,

I'm reduced to asking a newcomer's question: how can I make sed recurse down 
a directory tree? And while I'm at it, how do I change the field separator 
from / to enable me to search on that character?

I used to have a "SED and AWK" book, but it seems to have walked; and I 
can't see anything helpful from a Google search.

-- 
Rgds
Peter

Re: [gentoo-user] [OT] Use of sed

[Roy Wright]

On Jun 23, 2009, at 6:48 PM, Peter Humphrey wrote:

> Hello list,
>
> I'm reduced to asking a newcomer's question: how can I make sed  
> recurse down
> a directory tree? And while I'm at it, how do I change the field  
> separator
> from / to enable me to search on that character?

maybe something like:

find . -name '*' -exec sed {options} '{}' \;

HTH

Re: [gentoo-user] [OT] Use of sed

[Neil Bothwick]

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On Wed, 24 Jun 2009 00:48:07 +0100, Peter Humphrey wrote:

> I'm reduced to asking a newcomer's question: how can I make sed recurse
> down a directory tree?

You don't, that's not sed's job, which is to edit the text you give it.

Use find to generate a list of files for sed to work on.

> And while I'm at it, how do I change the field
> separator from / to enable me to search on that character?

By using something else, you don't need to tell sed, it works it out for
itself, just use something that isn't in your search string, : is a good
candidate. Or you can escape the / as \/ but this quickly degenerates
into the leaning matchstick appearance so beloved of Perl scripters. 


-- 
Neil Bothwick

Windows Error #01: No error... ...yet.

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Re: [gentoo-user] [OT] Use of sed

[Arttu V.]

On 6/24/09, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Wed, 24 Jun 2009 00:48:07 +0100, Peter Humphrey wrote:
>> And while I'm at it, how do I change the field
>> separator from / to enable me to search on that character?
>
> By using something else, you don't need to tell sed, it works it out for
> itself, just use something that isn't in your search string, : is a good
> candidate.

If I read his question right, he asked about just the simple matchers:
//. Perl solves this problem with the optional m in front (m//), so
you can do m:/foo: or m+/foo+, but I don't know of a similar toggle
for sed (well, I'm a sed newbie, so there might still be one).

I don't even think substituting the string with itself (s+/foo+/foo+)
would work as I think s/// will succeed every time, even when it
doesn't actually substitute anything, so maybe it cannot be used for
an "if-then" in sed either?

-- 
Arttu V.

Re: [gentoo-user] [OT] Use of sed

[Peter Humphrey]

On Wednesday 24 June 2009 02:36:08 Neil Bothwick wrote:
> On Wed, 24 Jun 2009 00:48:07 +0100, Peter Humphrey wrote:
> > I'm reduced to asking a newcomer's question: how can I make sed recurse
> > down a directory tree?
>
> You don't, that's not sed's job, which is to edit the text you give it.
>
> Use find to generate a list of files for sed to work on.

I'll do that. I was confused by a vague memory that there was a recursion 
flag somewhere, but I must have been mistaken.

> > And while I'm at it, how do I change the field
> > separator from / to enable me to search on that character?
>
> By using something else, you don't need to tell sed, it works it out for
> itself, just use something that isn't in your search string, : is a good
> candidate.

The man page makes no mention of that, and when I tried it anyway I got 
puzzling results, so I assumed it couldn't be done.

> Or you can escape the / as \/ but this quickly degenerates into the
> leaning matchstick appearance so beloved of Perl scripters. 

Horrors!

Thanks to all for the help. Maybe I should replace that text-book after all.

-- 
Rgds
Peter

Re: [gentoo-user] [OT] Use of sed

[Alan McKinnon]

On Wednesday 24 June 2009 11:34:18 Peter Humphrey wrote:
> On Wednesday 24 June 2009 02:36:08 Neil Bothwick wrote:
> > On Wed, 24 Jun 2009 00:48:07 +0100, Peter Humphrey wrote:
> > > I'm reduced to asking a newcomer's question: how can I make sed recurse
> > > down a directory tree?
> >
> > You don't, that's not sed's job, which is to edit the text you give it.
> >
> > Use find to generate a list of files for sed to work on.
>
> I'll do that. I was confused by a vague memory that there was a recursion
> flag somewhere, but I must have been mistaken.

sed doesn't do that.

sed takes a data stream, bashes it into shape, and outputs a (possibly 
modified) data stream. How you get the stream in, and what you do with it once 
it comes out, is up to you.

Possibly you were thinking of grep's recursion switch?

-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] [OT] Use of sed

[Peter Humphrey]

On Wednesday 24 June 2009 10:56:43 Alan McKinnon wrote:

> Possibly you were thinking of grep's recursion switch?

Perhaps. I'm not at my best in the mornings :-(

-- 
Rgds
Peter

Re: [gentoo-user] [OT] Use of sed

[Neil Bothwick]

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On Wed, 24 Jun 2009 12:03:19 +0100, Peter Humphrey wrote:

> Perhaps. I'm not at my best in the mornings :-(

Same here, and it's always morning somewhere :(


-- 
Neil Bothwick

Windows artificial intelligence: Unable to FORMAT A: Having a go at C:

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Re: [gentoo-user] [OT] Use of sed

[Alex Schuster]

Peter Humphrey writes:

> I'm reduced to asking a newcomer's question: how can I make sed recurse
> down a directory tree?

find . -type f -exec sed -i 's/foo/bar/g' '{}' \;

> And while I'm at it, how do I change the field
> separator from / to enable me to search on that character?

Well, just change it :)  It does not need to be a /, it is always the first 
character after the s. sed 's%foo%bar%g' will work just the same.

I used to use the § character because it is probably not being used in any 
of my file names, but maybe it was too special, because kate dropped it 
silently from my shell scripts I edited, and hell broke loose.

> I used to have a "SED and AWK" book, but it seems to have walked; and I
> can't see anything helpful from a Google search.

man sed answers your second question :)

	Wonko

Re: [gentoo-user] [OT] Use of sed

[Peter Humphrey]

On Wednesday 24 June 2009 12:28:05 Alex Schuster wrote:

> man sed answers your second question :)

 s/regexp/replacement/
     Attempt to match regexp against the pattern space. If successful,
     replace that portion matched with replacement. The replacement may
     contain the special character & to refer to that portion of the pattern
     space which matched, and the special escapes \1 through \9 to refer to
     the corresponding matching sub-expressions in the regexp.

No mention of using a different separator, and I couldn't find any other 
reference either. I did look before asking.

-- 
Rgds
Peter

Re: [gentoo-user] [OT] Use of sed

[Alex Schuster]

Peter Humphrey writes:

> On Wednesday 24 June 2009 12:28:05 Alex Schuster wrote:
> > man sed answers your second question :)
>
>  s/regexp/replacement/
>      Attempt to match regexp against the pattern space. If successful,
>      replace that portion matched with replacement. The replacement may
>      contain the special character & to refer to that portion of the
> pattern space which matched, and the special escapes \1 through \9 to
> refer to the corresponding matching sub-expressions in the regexp.
>
> No mention of using a different separator, and I couldn't find any other
> reference either. I did look before asking.

Oh, sorry. I thought the german man pages were just translations of the 
original man pages, but at least the one for sed is entirely different. It 
also mentions the flags like g to replace globally, not only the first 
instance.

Here is the OpenBSD man page for sed, it has more information. However, this 
sed is a little different from our GNU sed. For example, it does not have 
the -i option.

http://www.rocketaware.com/man/man1/sed.1.htm

	Wonko

Re: [gentoo-user] [OT] Use of sed

[Renat Golubchyk]

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Am Wed, 24 Jun 2009 15:18:02 +0100
schrieb Peter Humphrey <peter@humphrey.ukfsn.org>:
> On Wednesday 24 June 2009 12:28:05 Alex Schuster wrote:
> 
> > man sed answers your second question :)
> 
>  s/regexp/replacement/
>      Attempt to match regexp against the pattern space. If successful,
>      replace that portion matched with replacement. The replacement
> may contain the special character & to refer to that portion of the
> pattern space which matched, and the special escapes \1 through \9 to
> refer to the corresponding matching sub-expressions in the regexp.
> 
> No mention of using a different separator, and I couldn't find any
> other reference either. I did look before asking.

Man page is very short. Check the info pages for full documentation.
(Almost all tools from GNU userland have a short man page and a long
info page. At least that is what they say right at the bottom.)

Section 3.5 (The `s' Command) states in the first paragraph:

  The syntax of the `s' (as in substitute) command is
  `s/REGEXP/REPLACEMENT/FLAGS'.  The `/' characters may be uniformly
  replaced by any other single character within any given `s' command.
  The `/' character (or whatever other character is used in its stead)
  can appear in the REGEXP or REPLACEMENT only if it is preceded by a `\'
  character.


Cheers,
Renat

-- 
Probleme kann man niemals mit derselben Denkweise loesen,
durch die sie entstanden sind.
                                              (Einstein)

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Re: [gentoo-user] [OT] Use of sed

[Paul Hartman]

On Wed, Jun 24, 2009 at 9:49 AM, Renat Golubchyk<ragermany@gmx.net> wrote:
> Man page is very short. Check the info pages for full documentation.
> (Almost all tools from GNU userland have a short man page and a long
> info page. At least that is what they say right at the bottom.)

Also, I have these pages in my bookmarks:

http://www.grymoire.com/Unix/Sed.html

http://sed.sourceforge.net/sed1line.txt

because I can never remember how to do anything without looking it up.

[gentoo-user] Re: [OT] Use of sed

[Grant Edwards]

On 2009-06-24, Peter Humphrey <peter@humphrey.ukfsn.org> wrote:
> On Wednesday 24 June 2009 12:28:05 Alex Schuster wrote:
>
>> man sed answers your second question :)
>
>  s/regexp/replacement/
>      Attempt to match regexp against the pattern space. If successful,
>      replace that portion matched with replacement. The replacement may
>      contain the special character & to refer to that portion of the pattern
>      space which matched, and the special escapes \1 through \9 to refer to
>      the corresponding matching sub-expressions in the regexp.
>
> No mention of using a different separator, and I couldn't find
> any other reference either. I did look before asking.

Apparently that's something that everybody "just knows" so it
doesn't need to go in the man page. :)

It is, however, in the 'info' page:

   The s' Command
   ===============
   
      The syntax of the s' (as in substitute) command is
   s/REGEXP/REPLACEMENT/FLAGS'.  The /' characters may be
   uniformly replaced by any other single character within any
   given s' command. The /' character (or whatever other character
   is used in its stead) can appear in the REGEXP or REPLACEMENT
   only if it is preceded by a \' character.
   

-- 
Grant Edwards                   grante             Yow! BARBARA STANWYCK makes
                                  at               me nervous!!
                               visi.com