PHWinfo - Afficher un message

29/10/2006, 08h04

Barry Margolin wrote:
> In article <84iri4dtde.fsf@ripco.com>, comp@toddh.net (Todd H.)
> wrote:
>
>> transmute70@gmail.com writes:
>>
>>> Hello Everyone,
>>>
>>> I am a college student currently enrolled in a Unix class. Unix is in
>>> no way shape or form related to my major, and needless to say, I'm
>>> stumped.
>> Finally someone asking for with a homework question coming clean
>> and saying it's a homework question. Now this is the student I'd like
>> to learn the material.
>>
>>> The question I must answer is this:
>>>
>>> "Enter a single command-line that would find out the 5 files in/under
>>> /etc that contain the string 'ubuntu,' case insensitively, more than
>>> any other file in/under the /etc directory. Sort the list from most to
>>> least and throw away standard error."
>> Okay, so let's break this down. We need to find all files in /etc/
>> that ubuntu Ubuntu UBUNTU ubunTU whatever in them. Grep is the tool
>> for the job. grep ubuntu /etc/* of course. But that will do a case
>> senstive search. I'll bid you to consult
>> $ man grep
>>
>> to find the one option you need to add to the grep command to make the
>> search case insensitive.
>>
>> Now look at the output of that grep command will give you all the
>> lines of text in all the files in /etc with ubuntu in em. You may
>> even notice filenames at the beginning of each matching line.
>> Hrmm... maybe we can't just to a grep and maybe we need to start with
>> another command to operate on each file one at a time.
>
> You could also use the option to grep that tells it to just print the
> count of matches, rather than the matching lines themselves.
>
>> Big Hint: your one big ole command might start with a find /etc -exec
>> command and in the -exec clause, think about grep, wc, then maybe
>> piping that output somehow into sort finishing off with head -5
>> might be the ticket.
>
> If you use the option to print the count of matches, you don't need to
> use wc at all.
>
>>> I can do each part the question asks separately, but I've no idea how
>>> to put this all together to create a single working command. Any
>>> would be greatly appreciated.
>> I think the "one file at a time" operation that find /etc -exec
>> brings to the table might be the concept you're looking for.
>
> Not if you use the -c option to grep.
>

A problem with the grep -c approach is multiple instances of the
pattern on a single line. The -c outputs a count of "records",
i.e. lines, containing the pattern. While convenient, if multiple
instances of the pattern per line is likely, outputing the patterns
and counting them separately would be more accurate.

29/10/2006, 08h04	#4
Jon LaBadie Messages: n/a Hébergeur:	Re: Using the grep command to filter Barry Margolin wrote: > In article <84iri4dtde.fsf@ripco.com>, comp@toddh.net (Todd H.) > wrote: > >> transmute70@gmail.com writes: >> >>> Hello Everyone, >>> >>> I am a college student currently enrolled in a Unix class. Unix is in >>> no way shape or form related to my major, and needless to say, I'm >>> stumped. >> Finally someone asking for with a homework question coming clean >> and saying it's a homework question. Now this is the student I'd like >> to learn the material. >> >>> The question I must answer is this: >>> >>> "Enter a single command-line that would find out the 5 files in/under >>> /etc that contain the string 'ubuntu,' case insensitively, more than >>> any other file in/under the /etc directory. Sort the list from most to >>> least and throw away standard error." >> Okay, so let's break this down. We need to find all files in /etc/ >> that ubuntu Ubuntu UBUNTU ubunTU whatever in them. Grep is the tool >> for the job. grep ubuntu /etc/* of course. But that will do a case >> senstive search. I'll bid you to consult >> $ man grep >> >> to find the one option you need to add to the grep command to make the >> search case insensitive. >> >> Now look at the output of that grep command will give you all the >> lines of text in all the files in /etc with ubuntu in em. You may >> even notice filenames at the beginning of each matching line. >> Hrmm... maybe we can't just to a grep and maybe we need to start with >> another command to operate on each file one at a time. > > You could also use the option to grep that tells it to just print the > count of matches, rather than the matching lines themselves. > >> Big Hint: your one big ole command might start with a find /etc -exec >> command and in the -exec clause, think about grep, wc, then maybe >> piping that output somehow into sort finishing off with head -5 >> might be the ticket. > > If you use the option to print the count of matches, you don't need to > use wc at all. > >>> I can do each part the question asks separately, but I've no idea how >>> to put this all together to create a single working command. Any >>> would be greatly appreciated. >> I think the "one file at a time" operation that find /etc -exec >> brings to the table might be the concept you're looking for. > > Not if you use the -c option to grep. > A problem with the grep -c approach is multiple instances of the pattern on a single line. The -c outputs a count of "records", i.e. lines, containing the pattern. While convenient, if multiple instances of the pattern per line is likely, outputing the patterns and counting them separately would be more accurate.