Sed (Stream EDitor) - is command line text processor. It may be used to modify linux streams or files Popular cases of using sed is **replace text** if file. Example: `$ sed -i 's/regexp/replacement/g' fileNameToReplaceContent` Also you may replace text in stream using pipelines: `$ cat file_file | sed 's/regexp/replacement/g' ` Sed uses regular expressions Alternative os sed is [awk](https://infinite.education/view/awk)