# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/\d{1,2}[-\\/]\d{1,2}\s?[\-\\/]\s?\d{4}//gm;t' <<< "tetsts kmasjdkjsad kajsdkjasdkj kjadjaksd 45-12-2020 lkdlksldksd
asd sjdjska 10-11-1989 ksjdkds 1-11-1456
skdasdsa
dasdlkj kajsd kjaksdj ksadjk jsadkdj a 1/1 - 1899"
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