# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(<\w+)(\s*[\w-]+="[^"]+")*(\s*data-toggle="[^"]+")(\s*[\w-]+="[^"]+")*(\s*>)/$1$3$5/g;t' <<< "<td class=\"sky\" data-toggle=\"up\" id=\"heaven\" >
<td class=\"sky\" data-toggle=\"up\" id=\"heaven\" >
<td class=\"sky\" data-toggle=\"up\" id=\"heaven\" >
<td class=\"sky\" data-toggle=\"up\" id=\"heaven\" >
<td class=\"sky\" data-toggle=\"up\" id=\"heaven\" >
<td class=\"sky\" data-toggle=\"up\" id=\"heaven\" >
<td class=\"sky\" data-toggle=\"up\" id=\"heaven\" >
<td class=\"sky\" data-toggle=\"up\" id=\"heaven\" >
<a href=\"#\" data-toggle=\"modal\" data-target=\"xxxx\"></a>
<a href=\"#\"data-target=\"#available-assistance\" data-toggle=\"modal\" data-modal=\"yeah\"></a>
<a href=\"#\"data-target=\"#available-assistance\" data-toggle=\"modal\" data-modal=\"yeah\"></a>
"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html