Now if we look above, we see "<-:::" in the first line, "<-::" in the second, "->:::" in the fourth, now I must use sed to filter this so I get a output like:
Code:
<-:::
<-::
<-:::
->:::
->::
And this is the command ive written:
Code:
cat datasets/q13data.txt | sed -ne 's/.*\([-]*[<,>][-]*[:]*\).*/\1/;p'
The output should be as above, but i am getting:
Code:
<-:::
<-:::
<-:::
<-:::
>:::
Whats wrong ? well the first three, compare them to the above, and the second thing thats wrong is that when there is a "->" it only prints ">"
Like in my previous sed post, your problem is the leading greedy .*
Because here is no constant next character, it is most easy to switch to perl and its least greedy .*?
Code:
perl -ne 'print if s/.*?([-]*[<,>][-]*[:]*).*/$1/' file
Or let perl grep out a matching portion (always the first match, but need to add a line feed e.g. by means of the -l option)
Code:
perl -lne 'print $1 if /([-]*[<,>][-]*[:]*)/' file
Last edited by MadeInGermany; 06-22-2016 at 03:09 PM..
Reason: Another perl solution
sed
-n switch off default print
E sw. on extended regexes
's substitute command
/^ start of line
[^-<>]* any sequence of non "-", non "<", non ">" chars
| alternate regex separator ("OR" regexes)
[^:]* seq of non ":" chars
[:-<>]* any combination of "-><:" chars
[^:]*$ seq of non ":", EOL
// empty replacement string
g global flag (substitute ALL occurrences)
p print if substitution took place
' file
sed
-n switch off default print
E sw. on extended regexes
's substitute command
/^ start of line
[^-<>]* any sequence of non "-", non "<", non ">" chars
| alternate regex separator ("OR" regexes)
[^:]* seq of non ":" chars
[:-<>]* any combination of "-><:" chars
[^:]*$ seq of non ":", EOL
// empty replacement string
g global flag (substitute ALL occurrences)
p print if substitution took place
' file
I love you sir. I have a question on the " [^-<>]* ", the "^" here is the same as "!" (dont)? And why is the g flag needed ?
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