Escape a string for a sed replace pattern

The only three literal characters which are treated specially in the replace clause are / (to close the clause), \ (to escape characters, backreference, &c.), and & (to include the match in the replacement). Therefore, all you need to do is escape those three characters:

sed "s/KEYWORD/$(echo $REPLACE | sed -e 's/\\/\\\\/g; s/\//\\\//g; s/&/\\\&/g')/g"

Example:

$ export REPLACE="'\"|\\/><&!"
$ echo fooKEYWORDbar | sed "s/KEYWORD/$(echo $REPLACE | sed -e 's/\\/\\\\/g; s/\//\\\//g; s/&/\\\&/g')/g"
foo'"|\/><&!bar

Here is an example of an AWK I used a while ago. It is an AWK that prints new AWKS. AWK and SED being similar it may be a good template.

ls | awk '{ print "awk " "'"'"'"  " {print $1,$2,$3} " "'"'"'"  " " $1 ".old_ext > " $1 ".new_ext"  }' > for_the_birds

It looks excessive, but somehow that combination of quotes works to keep the ' printed as literals. Then if I remember correctly the vaiables are just surrounded with quotes like this: "$1". Try it, let me know how it works with SED.

These are the escape codes that I've found:

* = \x2a
( = \x28
) = \x29

" = \x22
/ = \x2f
\ = \x5c

' = \x27
? = \x3f
% = \x25
^ = \x5e

There are dozens of answers out there... If you don't mind using a bash function schema, below is a good answer. The objective below was to allow using sed with practically any parameter as a KEYWORD (F_PS_TARGET) or as a REPLACE (F_PS_REPLACE). We tested it in many scenarios and it seems to be pretty safe. The implementation below supports tabs, line breaks and sigle quotes for both KEYWORD and replace REPLACE.

NOTES: The idea here is to use sed to escape entries for another sed command.

CODE

F_REVERSE_STRING_R=""
f_reverse_string() {
    : 'Do a string reverse.

    To undo just use a reversed string as STRING_INPUT.

    Args:
        STRING_INPUT (str): String input.

    Returns:
        F_REVERSE_STRING_R (str): The modified string.
    '

    local STRING_INPUT=$1
    F_REVERSE_STRING_R=$(echo "x${STRING_INPUT}x" | tac | rev)
    F_REVERSE_STRING_R=${F_REVERSE_STRING_R%?}
    F_REVERSE_STRING_R=${F_REVERSE_STRING_R#?}
}

# [Ref(s).: https://stackoverflow.com/a/2705678/3223785 ]
F_POWER_SED_ECP_R=""
f_power_sed_ecp() {
    : 'Escape strings for the "sed" command.

    Escaped characters will be processed as is (e.g. /n, /t ...).

    Args:
        F_PSE_VAL_TO_ECP (str): Value to be escaped.
        F_PSE_ECP_TYPE (int): 0 - For the TARGET value; 1 - For the REPLACE value.

    Returns:
        F_POWER_SED_ECP_R (str): Escaped value.
    '

    local F_PSE_VAL_TO_ECP=$1
    local F_PSE_ECP_TYPE=$2

    # NOTE: Operational characters of "sed" will be escaped, as well as single quotes.
    # By Questor
    if [ ${F_PSE_ECP_TYPE} -eq 0 ] ; then
    # NOTE: For the TARGET value. By Questor

        F_POWER_SED_ECP_R=$(echo "x${F_PSE_VAL_TO_ECP}x" | sed 's/[]\/$*.^[]/\\&/g' | sed "s/'/\\\x27/g" | sed ':a;N;$!ba;s/\n/\\n/g')
    else
    # NOTE: For the REPLACE value. By Questor

        F_POWER_SED_ECP_R=$(echo "x${F_PSE_VAL_TO_ECP}x" | sed 's/[\/&]/\\&/g' | sed "s/'/\\\x27/g" | sed ':a;N;$!ba;s/\n/\\n/g')
    fi

    F_POWER_SED_ECP_R=${F_POWER_SED_ECP_R%?}
    F_POWER_SED_ECP_R=${F_POWER_SED_ECP_R#?}
}

# [Ref(s).: https://stackoverflow.com/a/24134488/3223785 ,
# https://stackoverflow.com/a/21740695/3223785 ,
# https://unix.stackexchange.com/a/655558/61742 ,
# https://stackoverflow.com/a/11461628/3223785 ,
# https://stackoverflow.com/a/45151986/3223785 ,
# https://linuxaria.com/pills/tac-and-rev-to-see-files-in-reverse-order ,
# https://unix.stackexchange.com/a/631355/61742 ]
F_POWER_SED_R=""
f_power_sed() {
    : 'Facilitate the use of the "sed" command. Replaces in files and strings.

    Args:
        F_PS_TARGET (str): Value to be replaced by the value of F_PS_REPLACE.
        F_PS_REPLACE (str): Value that will replace F_PS_TARGET.
        F_PS_FILE (Optional[str]): File in which the replacement will be made.
        F_PS_SOURCE (Optional[str]): String to be manipulated in case "F_PS_FILE" was
    not informed.
        F_PS_NTH_OCCUR (Optional[int]): [1~n] - Replace the nth match; [n~-1] - Replace
    the last nth match; 0 - Replace every match; Default 1.

    Returns:
        F_POWER_SED_R (str): Return the result if "F_PS_FILE" is not informed.
    '

    local F_PS_TARGET=$1
    local F_PS_REPLACE=$2
    local F_PS_FILE=$3
    local F_PS_SOURCE=$4
    local F_PS_NTH_OCCUR=$5
    if [ -z "$F_PS_NTH_OCCUR" ] ; then
        F_PS_NTH_OCCUR=1
    fi

    local F_PS_REVERSE_MODE=0
    if [ ${F_PS_NTH_OCCUR} -lt -1 ] ; then
        F_PS_REVERSE_MODE=1
        f_reverse_string "$F_PS_TARGET"
        F_PS_TARGET="$F_REVERSE_STRING_R"
        f_reverse_string "$F_PS_REPLACE"
        F_PS_REPLACE="$F_REVERSE_STRING_R"
        f_reverse_string "$F_PS_SOURCE"
        F_PS_SOURCE="$F_REVERSE_STRING_R"
        F_PS_NTH_OCCUR=$((-F_PS_NTH_OCCUR))
    fi

    f_power_sed_ecp "$F_PS_TARGET" 0
    F_PS_TARGET=$F_POWER_SED_ECP_R
    f_power_sed_ecp "$F_PS_REPLACE" 1
    F_PS_REPLACE=$F_POWER_SED_ECP_R

    local F_PS_SED_RPL=""
    if [ ${F_PS_NTH_OCCUR} -eq -1 ] ; then
    # NOTE: We kept this option because it performs better when we only need to replace
    # the last occurrence. By Questor

        # [Ref(s).: https://linuxhint.com/use-sed-replace-last-occurrence/ ,
        # https://unix.stackexchange.com/a/713866/61742 ]
        F_PS_SED_RPL="'s/\(.*\)$F_PS_TARGET/\1$F_PS_REPLACE/'"
    elif [ ${F_PS_NTH_OCCUR} -gt 0 ] ; then
        # [Ref(s).: https://unix.stackexchange.com/a/587924/61742 ]
        F_PS_SED_RPL="'s/$F_PS_TARGET/$F_PS_REPLACE/$F_PS_NTH_OCCUR'"
    elif [ ${F_PS_NTH_OCCUR} -eq 0 ] ; then
        F_PS_SED_RPL="'s/$F_PS_TARGET/$F_PS_REPLACE/g'"
    fi

    # NOTE: As the "sed" commands below always process literal values for the "F_PS_TARGET"
    # so we use the "-z" flag in case it has multiple lines. By Quaestor
    # [Ref(s).: https://unix.stackexchange.com/a/525524/61742 ]
    if [ -z "$F_PS_FILE" ] ; then
        F_POWER_SED_R=$(echo "x${F_PS_SOURCE}x" | eval "sed -z $F_PS_SED_RPL")
        F_POWER_SED_R=${F_POWER_SED_R%?}
        F_POWER_SED_R=${F_POWER_SED_R#?}
        if [ ${F_PS_REVERSE_MODE} -eq 1 ] ; then
            f_reverse_string "$F_POWER_SED_R"
            F_POWER_SED_R="$F_REVERSE_STRING_R"
        fi
    else
        if [ ${F_PS_REVERSE_MODE} -eq 0 ] ; then
            eval "sed -i -z $F_PS_SED_RPL \"$F_PS_FILE\""
        else
            tac "$F_PS_FILE" | rev | eval "sed -z $F_PS_SED_RPL" | tac | rev > "$F_PS_FILE"
        fi
    fi

}

MODEL

f_power_sed "F_PS_TARGET" "F_PS_REPLACE" "" "F_PS_SOURCE"
echo "$F_POWER_SED_R"

EXAMPLE

f_power_sed "{ gsub(/,[ ]+|$/,\"\0\"); print }' ./  and eliminate" "[ ]+|$/,\"\0\""  "" "Great answer (+1). If you change your awk to awk '{ gsub(/,[ ]+|$/,\"\0\"); print }' ./  and eliminate that concatenation of the final \", \" then you don't have to go through the gymnastics on eliminating the final record. So: readarray -td '' a < <(awk '{ gsub(/,[ ]+/,\"\0\"); print; }' <<<\"$string\") on Bash that supports readarray. Note your method is Bash 4.4+ I think because of the -d in readar"
echo "$F_POWER_SED_R"

IF YOU JUST WANT TO ESCAPE THE PARAMETERS TO THE SED COMMAND

MODEL

# "TARGET" value.
f_power_sed_ecp "F_PSE_VAL_TO_ECP" 0
echo "$F_POWER_SED_ECP_R"

# "REPLACE" value.
f_power_sed_ecp "F_PSE_VAL_TO_ECP" 1
echo "$F_POWER_SED_ECP_R"

IMPORTANT: If the strings for KEYWORD and/or replace REPLACE contain tabs or line breaks you will need to use the "-z" flag in your "sed" command. More details here.

EXAMPLE

f_power_sed_ecp "{ gsub(/,[ ]+|$/,\"\0\"); print }' ./  and eliminate" 0
echo "$F_POWER_SED_ECP_R"
f_power_sed_ecp "[ ]+|$/,\"\0\"" 1
echo "$F_POWER_SED_ECP_R"

NOTE: The f_power_sed_ecp and f_power_sed functions above was made available completely free as part of this project ez_i - Create shell script installers easily!.

sed is typically a mess, especially the difference between gnu-sed and bsd-sed

might just be easier to place some sort of sentinel at the sed side, then a quick pipe over to awk, which is far more flexible in accepting any ERE regex, escaped hex, or escaped octals.

e.g. OFS in awk is the true replacement ::

date | sed -E 's/[0-9]+/\xC1\xC0/g' |  

          mawk NF=NF FS='\xC1\xC0' OFS='\360\237\244\241'  

 1  Tue Aug   :: EDT 

(tested and confirmed working on both BSD-sed and GNU-sed - the emoji isn't a typo that's what those 4 bytes map to in UTF-8 )

don't forget all the pleasure that occur with the shell limitation around " and '

so (in ksh)

Var=">New version of \"content' here <"
printf "%s" "${Var}" | sed "s/[&\/\\\\*\\"']/\\&/g' | read -r EscVar

echo "Here is your \"text\" to change" | sed "s/text/${EscVar}/g"

I have an improvement over the sedeasy function, which WILL break with special characters like tab.

function sedeasy_improved {
    sed -i "s/$(
        echo "$1" | sed -e 's/\([[\/.*]\|\]\)/\\&/g' 
            | sed -e 's:\t:\\t:g'
    )/$(
        echo "$2" | sed -e 's/[\/&]/\\&/g' 
            | sed -e 's:\t:\\t:g'
    )/g" "$3"
}

So, whats different? $1 and $2 wrapped in quotes to avoid shell expansions and preserve tabs or double spaces.

Additional piping | sed -e 's:\t:\\t:g' (I like : as token) which transforms a tab in \t.

An easier way to do this is simply building the string before hand and using it as a parameter for sed

rpstring="s/KEYWORD/$REPLACE/g"
sed -i $rpstring  test.txt