I have a text file as follows:
test1,test2,test3 test4,test5 test6,test7,test8,test9,test10 test11,test12,test13,test14 How can I replace commas with semicolons, starting with the second one (and continuing to the last one)?
I want to get output as follows:
test1,test2;test3 test4,test5 test6,test7;test8;test9;test10 test11,test12;test13;test14 This can be done with this,
$ sed -e 's/,/;/g' -e 's/;/,/1' infile test1,test2;test3 test4,test5 test6,test7;test8;test9;test10 test11,test12;test13;test14 Explanation
s/,/;/g replaces all occurrence of , with ;
s/;/,/1 replaces the first occurrence of ; with ,
If you have GNU sed, you can also try this simple and handy,
sed 's/,/;/2g' infile sed 's/,/;/2g' on GNU sed, cool one! If the input might already have semicolons in it, we have to be careful:
$ sed 's/,/\n/g; s/\n/,/; s/\n/;/g' input test1,test2;test3 test4,test5 test6,test7;test8;test9;test10 test11,test12;test13;test14 Since sed reads the input line-by-line, there will be no newline characters in normal input. So, we can replace all the commas with newlines and we know that there will be no confusion. Next we restore the first newline back to a comma. Lastly, we replace all remaining newlines with a semicolon.
In more detail:
s/,/\n/g replaces all commas with newlines.
s/\n/,/ replaces the first newline with a comma.
s/\n/;/g replaces all remaining newlines with semicolons.
sed 's/,/\n/; s/,/;/g; s/\n/,/', which is very similar to your answer, except mine has only one global command. Can you identify a situation where your command works better than mine? Using awk:
awk '{gsub(",", ";"); sub(";", ","); print}' file.txt gsub(",", ";") replaces all , with ;
sub(";", ",") replaces the first ; with ,
Example:
% cat file.txt test1,test2,test3 test4,test5 test6,test7,test8,test9,test10 test11,test12,test13,test14 % awk '{gsub(",", ";"); sub(";", ","); print}' file.txt test1,test2;test3 test4,test5 test6,test7;test8;test9;test10 test11,test12;test13;test14 
$ cat ip.txt test1,test2,test3 test4,test5 test6,test7,test8,test9,test10 test11,test12,test13,test14 test15 $ perl -F, -ane 'print "$F[0]"; print ",".join(";",@F[1..$#F]) if($#F > 0)' ip.txt test1,test2;test3 test4,test5 test6,test7;test8;test9;test10 test11,test12;test13;test14 test15
Another way:
perl -F'/(,)/,$_,2' -ane '$F[2] =~ s/,/;/g; print @F' /(,)/,$_,2 split $_ (the input line) into two based on , Since (,) is used, it captures the separator as well resulting in three elements as explained below$F[0] gets first field, $F[1] will get , if present$F[2] gets remaining fields if present
Yet another way, emulating sed 's/,/;/2g'
perl -pe '$c=0; s/,/++$c<2 ? $& : ";"/ge' ip.txt e modifier allows Perl code in replacement section