Ed Morton schreef:
> On 2/8/2008 6:50 AM, Luuk wrote:
>> "Ed Morton" <morton@[EMAIL PROTECTED]
> schreef in bericht
>> news:47AB6DD4.5060009@[EMAIL PROTECTED]
>>
>>> On 2/7/2008 2:37 PM, Kurda Yon wrote:
>>>
>>>> Hi,
>>>>
>>>> I have the following problem. In my text-file each line has the
>>>> following format:
>>>>
>>>> field_1 field_2 ... field_n (tf. field_1a, field_2a ... field_ka)
>>>>
>>>> And I need to extract field_1a, field_2a, ...and field_ka. Here I see
>>>> several subproblems which I cannot solve:
>>>> 1. Different lines have different number of fields before the
>>>> (tf. ... ) block.
>>>> 2. (tf. ... ) blocks also contain different number of fields.
>>>> 3. There is no space between "field_ka" and ")". And I want to remove
>>>> ")".
>>>>
>>>> Can this problem be easily solved in awk?
>>> Yes:
>>>
>>> $ cat file
>>> field_1 field_2 ... field_n (tf. field_1a, field_2a ... field_ka)
>>> $ awk 'gsub(/.*\(....|\)$/,"")1' file
>>> field_1a, field_2a ... field_ka
>>>
>>> Regards,
>>>
>>> Ed.
>>>
>>
>> could someone explain the '1' in "$ awk 'gsub(/.*\(....|\)$/,"")1'
file" ?
>
> It makes sure that even if the input record is empty (in which case
gsub() will
> return 0) the eventual condition being tested by awk is
non-zero/non-null so
> that printing the current record occurs even in that case.
>
> The operator used to combine the result of the gsub() with the "1" is
> string-concatenation so you can put anything after the gsub() to get a
non-null
> resultant string, even zero (to get the string "00") or the null string
(to get
> the string "0" as opposed to the number zero).
>
>> awk does not seem to do anything with it...
>> or is it just a typo?
>
> No. Look:
>
> $ cat file
> a
>
> c
> $ awk 'sub(/./,NR)' file
> 1
> 3
> $ awk 'sub(/./,NR)1' file
> 1
>
> 3
>
>> but awk also does not complain when i type:
>> $ awk 'gsub(/.*\(....|\)$/,"")g' file
>
> Right. In that case it evaluates the unassigned variable "g" to the null
string
> "" which is string-concatenated with the zero result of sub() to give a
non-null
> "0" string:
>
> $ awk 'sub(/./,NR)g' file
> 1
>
> 3
>
> Regards,
>
> Ed.
>
i must have skipped that part of the man-page....
normally i use to do:
awk '{ sub(/./,NR); print $0 }' file
which i indeed something longer... ;-)
--
Luuk
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