Sed

Edit in place¶

sed -i 's/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g' filename

Match only the word¶

\b in regex is used to match word boundaries (i.e. the location between the first word character and non-word character).

sed -i 's/\bsuper_specific_phrase\b/STRING_TO_REPLACE_IT/g' filename