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.
|
