hello all! I'd like to ask if there's a unix command that could delete
parts of the file given a string. Example:
Given: File1 which contains
--testing--
test123
--testing--
--hello--
world
--hello--

If my string is hello, the output would be another file or the same
file but without the hello block. So, the output would be
--testing--
test123
--testing--

if anybody knows please help! thanks!

In article <304f3217.0307071251.7293969a@posting.google.com>,
 wyl_lyf@yahoo.com (melissa_benkyo) wrote:

> hello all! I'd like to ask if there's a unix command that could delete
> parts of the file given a string. Example:
> Given: File1 which contains
> --testing--
> test123
> --testing--
> --hello--
> world
> --hello--
> 
> If my string is hello, the output would be another file or the same
> file but without the hello block. So, the output would be
> --testing--
> test123
> --testing--
> 
> if anybody knows please help! thanks!

You could write a script in perl to exclude all lines which contain 
"hello".  Same with awk.

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melissa_benkyo wrote:
>
> If my string is hello, the output would be another file or the same
> file but without the hello block.


It sounds like you want to eliminate a "block" of text, starting and ending
with a key word on a line of its own.  That's not going to be accomplished
with a simple grep as has been suggested, but there are a few equally easy
ways of accomplishing this.

Before we go there, though....might this be a homework assignment that
you're hoping to accomplish today?

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In article <304f3217.0307071251.7293969a@posting.google.com>, melissa_benkyo wrote:
> hello all! I'd like to ask if there's a unix command that could delete
> parts of the file given a string. Example:
> Given: File1 which contains
> --testing--
> test123
> --testing--
> --hello--
> world
> --hello--
> 
> If my string is hello, the output would be another file or the same
> file but without the hello block. So, the output would be
> --testing--
> test123
> --testing--

If you want to lose the --hello-- / --hello-- limited block, you could
try if sgrep (http://www.cs.helsinki.fi/u/jjaakkol/sgrep.html) does
what you want.

	Taneli

* melissa_benkyo <wyl_lyf@yahoo.com>:
> hello all! I'd like to ask if there's a unix command that could delete
> parts of the file given a string. Example:
> Given: File1 which contains
> --testing--
> test123
> --testing--
> --hello--
> world
> --hello--
> 
> If my string is hello, the output would be another file or the same
> file but without the hello block. So, the output would be
> --testing--
> test123
> --testing--

I assume you want to delete all hello blocks including the "--hello--"
lines. Then

  sed -e '/--hello--/,/--hello--/d' < infile > outfile

should suffice. If the command should modify the file rather than
writing a new one, 

  perl -i -ne 'print unless /--hello--/ ... /--hello--/' thefile

or

  perl -0777 -i -pe 's/--hello--.*?--hello--\n//gs' thefile

can mimick that (Perl internally writes a new file and renames it).

 -ooo- Andy

melissa_benkyo wrote:
> hello all! I'd like to ask if there's a unix command that could delete
> parts of the file given a string. Example:
> Given: File1 which contains
> --testing--
> test123
> --testing--
> --hello--
> world
> --hello--
> 
> If my string is hello, the output would be another file or the same
> file but without the hello block. So, the output would be
> --testing--
> test123
> --testing--
> 
> if anybody knows please help! thanks!


awk '
BEGIN { pr=1 }
{
     if (pr==1){
         if($0 ~ "--hello--") pr=0
         else print
     }
     else if($0 ~ "--hello--") pr=1
}'

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but not limited to telepathy  without the benevolence of the author.

In article <1057697526.951081@smirk>,
James T. Dennis <jadestar@idiom.com> wrote:
....
> These awk scripts are just filters; you'd have to use redirection,
> temporary files and renaming (a shell script wrapper around these
> awk commands) to change your file.  Alternatively you can use the
> perl -i (in situ edit) switch to force your changes directly into
> the file.  I'll leave that (and concerns about robustness and error
> handling --- like if the perl script is killed abruptly in mid-file)
> as exercises to the original poster.

Note that Perl does *not* do in-situ editing.  It is just pretend (aka,
syntactic sugar).  Perl's -i switch is 100% identical to a wrapper around
an AWK script like this:

	tmp=/tmp/tmp.$$
	awk ... infile > $tmp
	mv $tmp infile

(with, of course, the added proviso that -ibak leaves the original file
intact as foo.bak - again, easily enough implemented in a shell wrapper)

Note that the file systems of Unix and Unix-like systems (including
DOS/Windows) simply do not support in-situ editing - one way or another,
the file has to be re-written from scratch.  Now, MTS, on the other hand...

Note also that using "ex" as a scripting utility comes closest (*), but
even then, a temp file is involved (it is kept very well hidden from the
user, however).

(*) And, incidentally, is a good solution to a lot of these Usenet queries,
like, e.g., "how do I delete the last 3 lines of a file?"  Generally, "ex"
solutions are clearer and more robust than the typical sed/perl line noise.

Kenny McCormack <gazelle@yin.interaccess.com> wrote:
> In article <1057697526.951081@smirk>,
> James T. Dennis <jadestar@idiom.com> wrote:
> ...
>> These awk scripts are just filters; you'd have to use redirection,
>> temporary files and renaming (a shell script wrapper around these
>> awk commands) to change your file.  Alternatively you can use the
>> perl -i (in situ edit) switch to force your changes directly into
>> the file.  I'll leave that (and concerns about robustness and error
>> handling --- like if the perl script is killed abruptly in mid-file)
>> as exercises to the original poster.

> Note that Perl does *not* do in-situ editing.  It is just pretend (aka,
> syntactic sugar).  Perl's -i switch is 100% identical to a wrapper around
> an AWK script like this:

> 	tmp=/tmp/tmp.$$
> 	awk ... infile > $tmp
> 	mv $tmp infile

> (with, of course, the added proviso that -ibak leaves the original file
> intact as foo.bak - again, easily enough implemented in a shell wrapper)

> Note that the file systems of Unix and Unix-like systems (including
> DOS/Windows) simply do not support in-situ editing - one way or another,
> the file has to be re-written from scratch.  Now, MTS, on the other hand...

Slight misunderstanding seems to have slipped in. UN*X allows perfectly well
a process to read and write ( also known as "update" ) a file. There 
is nothing strange about that. 


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