I don't think it's possible with echo command, use the following sed approach instead:

sed -i '$ s/$/abc/' file.txt

• $ - indicate the last record/line
• s/$/abc/ - substitute the end of the line $ with substring abc (for the last record)

I don't think it's possible with echo command, use the following sed approach instead:

sed -i '$ s/$/abc/' file.txt

• -i - modify the file inplace
• $ - indicate the last record/line
• s/$/abc/ - substitute the end of the line $ with substring abc (for the last record)

I don't think it's possible with echo command, use the following sed approach instead:

sed -i '$ s/$/abc/' file.txt

• $ - indicate the last record
• s/$/abc/ - substitute the end of the string $ with substring abc (for the last record)

I don't think it's possible with echo command, use the following sed approach instead:

sed -i '$ s/$/abc/' file.txt

• $ - indicate the last record/line
• s/$/abc/ - substitute the end of the line $ with substring abc (for the last record)