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grep with regular expression optional value

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# 1  
Old 08-06-2009
grep with regular expression optional value
field 12345 12345
field 12345
field 12345 123456

last fleld (from three) is optional, but if it occures It has to be composed only of nummbers and maximum 5 positions long.

If I use:

Code:
grep "^field [0-9]\{5\}"

I get:

field 12345 12345
field 12345
field 12345 123456

But I wont to get just:

field 12345 12345
field 12345

I thought that this will work, but it doesent:
Code:
grep "^field [0-9]\{5\} [0-9]\{0,5\}"

# 2  
Old 08-06-2009
try..
Code:
grep "^field [0-9]\{5\} [0-9]\{0,5\}$" file



---------- Post updated at 10:20 PM ---------- Previous update was at 10:19 PM ----------

remember grep search matching lines. so you should tell it to stop at a certainpoint
Code:
-bash-3.2$ cat file
a
ab
abc
-bash-3.2$ grep ab file
ab
abc
-bash-3.2$ grep ab$ file
ab
-bash-3.2$

# 3  
Old 08-06-2009
Quote:
Originally Posted by ryandegreat25
try..
Code:
grep "^field [0-9]\{5\} [0-9]\{0,5\}$" file

---------- Post updated at 10:20 PM ---------- Previous update was at 10:19 PM ----------

remember grep search matching lines. so you should tell it to stop at a certainpoint
Code:
-bash-3.2$ cat file
a
ab
abc
-bash-3.2$ grep ab file
ab
abc
-bash-3.2$ grep ab$ file
ab
-bash-3.2$

Great, thanks this works. But what if this field is not the last one in the row. Like this:

field 12345 12345 a
field 12345 a
field 12345 123456 a

In that case this ´guy´ dos not work:
Code:
grep "^field [0-9]\{5\} [0-9]\{0,5\} [a-z]$" file

# 4  
Old 08-06-2009
what output you want then?
# 5  
Old 08-06-2009
Quote:
Originally Posted by ryandegreat25
what output you want then?
I wont:

field 12345 12345 a
field 12345 a

But with
Code:
grep "^field [0-9]\{5\} [0-9]\{0,5\} [a-z]$" file

I get:

field 12345 12345 a
# 6  
Old 08-06-2009
this is quite complex.. i couldnt think of anything beside awk.
Code:
awk '{if (length($3) <= 5) {print $0}}' file

# 7  
Old 08-06-2009
Quote:
Originally Posted by necroman08
...
But what if this field is not the last one in the row. Like this:

field 12345 12345 a
field 12345 a
field 12345 123456 a
...
I guess in this case, your conditions are:

(i) Print the line if the number of fields is less than 3
(ii) If the 3rd field exists, print the line if it does not consist of any digits. Its length does not matter here.
(iii) If the 3rd field exists, print the line if it consists ONLY of digits and has a length of 5 or less.
(iv) There can be more than 3 fields, and the line will be printed as long as rules (ii) and (iii) are satisfied.

So for the data below, you want to display lines 1,2,4 and 7:

Code:
$
$ cat -n data.txt
     1  field 12345 12345 a
     2  field 12345 a
     3  field 12345 123456 a
     4  field 12345
     5  field 12345 12aQ~
     6  field 12345 12aQ~ 123
     7  field 12345 1340 4578 abc AB#xy2
$
$

Perl script:

Code:
$
$ perl -ne '@a=split; $f=$a[2]; ($x=$f)=~s/\d//g; ($y=$f)=~s/\D//g;
>           print if ( $#a<2 or
>                      ($#a>=2 and $x eq $f) or
>                      ($#a>=2 and $y eq $f and length($f)<=5)
>                    )' data.txt
field 12345 12345 a
field 12345 a
field 12345
field 12345 1340 4578 abc AB#xy2
$
$

tyler_durden
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