https://www.gnu.org/software/sed/manual/sed.html

• Replace the first occurrence of a regular expression in each line of a file, and print the result:

`sed 's/{{regular<sub>expression</sub>}}/{{replace}}/' {{filename}}`

• Replace all occurrences of an extended regular expression in a file, and print the result:

`sed -r 's/{{regular<sub>expression</sub>}}/{{replace}}/g' {{filename}}`

• Replace all occurrences of a string in a file, overwriting the file (i.e. in-place):

`sed -i 's/{{find}}/{{replace}}/g' {{filename}}`

• Replace only on lines matching the line pattern:

`sed '{{line<sub>pattern</sub>}}/s/{{find}}/{{replace}}' {{filename}}`

• Delete lines matching the line pattern:

`sed '/{{line<sub>pattern</sub>}}/d' {{filename}}`

• Print the first 11 lines of a file:

`sed 11q {{filename}}`

• Apply multiple find-replace expressions to a file:

`sed -e 's/{{find}}/{{replace}}/' -e 's/{{find}}/{{replace}}/' {{filename}}`

• Replace separator `/` by any other character not used in the find or replace patterns, e.g. `#`:

`sed 's#{{find}}#{{replace}}#' {{filename}}`

from https://github.com/tldr-pages/tldr/blob/main/pages/common/sed.md