split lines and print it to new line for certain character

sed -E -e 's/ (ABC)/\n\1/g' 

The sed command replaces any instance of ABC with a newline followed by ABC. It uses the () to capture part of the match (ABC without the leading space) and \1 to include it in the replacement.

e.g.

$ echo 'ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955'| sed -E -e 's/ (ABC)/\n\1/g' ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955 

With sed:

$ sed -e 's/ ABC/\ ABC/g' <file ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955 

Try this awk.

echo "ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955" | awk '{for(i=1;i<=NF;i++) if(match($i,"ABC")>0) line=line "\n"$i;else line=line $i; sub("^\n","",line); print line}' 

Creates a line with all fields, adding in front of the fields that begin with "ABC" a line break. Finally it eliminates the first line break and prints

You can also do it with paste and tr:

$ echo 'ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955' | tr ' ' '\n' | paste -d ' ' - - ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955 

Using Perl

~$ printf "ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955\n" | perl -pe 's/\h+ABC/\ ABC/g' ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955 

Above Perl answer is most similar to the excellent sed answer posted by @cuonglm. In Perl-family languages, the -pe commandline flags give sed-like behavior, i.e. execution, linewise-with-autoprinting. the \h+ atom stands for horizontal whitespace.

Using Raku (formerly known as Perl_6)

~$ printf "ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955\n" | raku -pe 's:g/ \h+ ABC/{"\n"}ABC/' ABC123xxx:: 2345 ABC345yyy:: 5678 ABC986zzz:: 7955 

The above Raku answer (formerly Perl6) is almost identical the Perl(5) answer. However to use the :global modifier, it gets moved to the head of the s:g/// idiom. Also, if you want run code within the replacement-half [ example {"\n"} ], simply enclose it in curlie braces, which helps with readability--very easy to see a \n newline is being inserted.

Perl References:
https://perldoc.perl.org
https://www.perl.org

Raku References:
https://docs.raku.org
https://raku.org