Count the number of occurrence of pattern in a file using Perl. perl -e '$_ = <>; print scalar ( () = m/needle/g ), "\n"' #Perl #Perloneliner #Count #Occurrence
Search and replace the string 'this' with the string 'that' in the file filename. perl -p -i -e 's/this/that/g' filename #Perl #Trick #PerlOneLiner #Tipsoftheday #Replace #FindandReplace
Extract sequence by using Ids file (assuming one ids in a line): perl -ne 'if(/^>(\S+)/){$c=$i{$1}}$c?print:chomp;$i{$_}=1 if @ARGV' ids.file fasta.file #PerlTricks #PerlOneliner #Perl #Extract #Ids #