How to append end of every line with the line itself

awksed

This is in file.txt:

redcar
bluecar
greencar

Im looking for ways to make it become:

redcar redcar
bluecar bluecar
greencar greencar

I've tried many ways using sed with no luck

Here is a simple solution using paste:

paste -d ' ' file.txt file.txt

Here are three options:

awk and its variants (gawk, mawk etc.):

awk '{if(NR==1){print $0,"| Place"} else{print $0,"| Paris"}}' file.txt

Perl:

perl -lne '$.==1 ? print "$_ | Place" : print "$_ | Paris"' file.txt

sed

sed '1 s/$/ | Place/; 1! s/$/ | Paris/' file.txt

You almost had it with:

~~sed -i '/Hello/{/World/a} appendstring' file~~

You need to separate your arguments. Use -e, like so:

sed -i -e '/Hello/{/World/a appendstring' -e '}' file

Note that using the append command without a newline is a GNU extension, as is the -i switch.

To do this more portably, and considering as well the possibility of multiple strings to match, try:

sed '/multiple/{/words/{/to/{/match/ s/$/append this/;};};}' file > newfile
mv newfile file

Since you're using GNU Sed already, just use:

sed -i -e '/multiple/{/words/{/to/{/match/ a append this' -e 'a and also this' -e 'a oh and this too' -e '};};}' file