Substitution in text file **without** regular expressions

export FIND='find this'
export REPLACE='replace with this'
ruby -p -i -e "gsub(ENV['FIND'], ENV['REPLACE'])" path/to/file

This is the only 100% safe solution here, because:

• It's a static substition, not a regexp, no need to escape anything (thus, superior to using sed)
• It won't break if your string contains } char (thus, superior to a submitted Perl solution)
• It won't break with any character, because ENV['FIND'] is used, not $FIND. With $FIND or your text inlined in Ruby code, you could hit a syntax error if your string contained an unescaped '.

When you don't need the power of regular expressions, don't use it. That is fine.
But, this is not really a regular expression.

sed 's|literal_pattern|replacement_string|g'

So, if / is your problem, use | and you don't need to escape the former.

PS: About the comments, also see this Stackoverflow answer on Escape a string for sed search pattern.

Update: If you are fine using Perl try it with \Q and \E like this,

 perl -pe 's|\Qliteral_pattern\E|replacement_string|g'

_{@RedGrittyBrick has also suggested a similar trick with stronger Perl syntax in a comment here or here}

You can do it converting the patterns to their escaped form automatically. Like this:

keyword_raw=$'1\n2\n3'
keyword_regexp="$(printf '%s' "$keyword_raw" | sed -e 's/[]\/$*.^|[]/\\&/g' | sed ':a;N;$!ba;s,\n,\\n,g')"
# keyword_regexp is now '1\/2\/3'

replacement_raw=$'2\n3\n4'
replacement_regexp="$(printf '%s' "$replacement_raw" | sed -e 's/[\/&]/\\&/g' | sed ':a;N;$!ba;s,\n,\\n,g')"
# replacement_regexp is now '2\/3\/4'

echo $'a/b/c/1\n2\n3/d/e/f' | sed -e "s/$keyword_regexp/$replacement_regexp/"
# the last command will print 'a/b/c/2\n3\n4/d/e/f'

Credits for this solutions goes here: https://stackoverflow.com/questions/407523/escape-a-string-for-a-sed-replace-pattern

Note1: this only works for non-empty keywords. Empty keywords are not accepted by sed (sed -e 's//replacement/').

Note2: unfortunately, I don't know a popular tool that would NOT use regexp-s to solve the problem. You can write such a tool in Rust or C, but it's not there by default.

You could also use perl's \Q mechanism to "quote (disable) pattern metacharacters"

perl -pe 'BEGIN {$text = q{your */text/?goes"here"}} s/\Q$text\E/replacement/g'