Hi, all
I have a file a.txt contains lines like below:
mez:Mtc_0001 glycosyltransferase
mez:Mtc_0002 feoA; Iron dependent transcriptional regulator; K03709 DtxR family transcriptional regulator, Mn-dep
mez:Mtc_0003 feoB; ferrous iron transporter FeoB; K04759 ferrous iron transport protein B
(there is multi-space between mtc_000x and things following)
I want to use Perl to do following things, but I just begin to learn Perl,
1) delete all mez in all lines at the begining;
2) foreach $line (@line) {separate "\t" but not multi-space or ";"}
3) print and store the results in a new b.txt file and keep the a.txt file unchanged.
could you give some suggestions on this.
thanks!
•
written
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liupfskygre
perl -ne '$_=~s/^mez://;$_=~s/;\s+/\t/g;print "$_\n";' a.txt > b.txt
use perl:
perl -ne 'your perl code'
delete all "mez:" at the beginning:
$_=~s/^mez://;
change all ";" followed by spaces to "\t":
$_=~s/;\s+/\t/g;
write result to new file without changing the input file:
> b.txt
thanks
there is multi-space between mtc_000x and things following, how to change those spaces into tab "\t" too, like $_=~s/#multi-spaces#/\t/, right? I review the book, and now I know the use of s///, but what do "=~" symbol and "^"mean?
David Langenberger's s/;\s+/\t/g substitutes a tab for a semi-colon followed by one or more whitespaces. However, you also want the same tab substitution for a the whitespaces after the mtc_000x pattern. You can use the above--with just a couple of changes--right after the first substitution:
s/\s+/\t/
This will replace the first set of whitespaces with a tab. Given the above, final the oneliner could be:
perl -p -ne 's/^mez://;s/\s+/\t/;s/;\s+/\t/g' a.txt > b.txt
The =~ symbol is Perl's regex binding operator. The ^ notation above is an anchor which means "from the beginning of the line."
Well done, and nice explanation of the parts (+1)! You can, however, do the following:
perl -p -ne 's/^mez://;s/;\s+/\t/g' a.txt > b.txt
As you likely know, your s/// implicitly operates on $_, so it's not necessary to explicitly use $_; -p prints the line.
Nit: "... followed by spaces..." -> s/(?=spaces)/white/
Thanks! It worked well!
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why perl ? one
sedwould ok.thanks, I am also trying to learn perl but could not figure things out now. maybe it would be figured out after I go through regular expression chapter.