sed

Source: https://www.linux.org/threads/why-i-love-sed-and-a-clear-practical-beginners-guide-to-using-it.43651/

Excerpt from man page

Sed is a stream editor. A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline). While in some ways similar to an editor which permits scripted edits (such as ed), sed works by making only one pass over the input(s), and is consequently more efficient. But it is sed’s ability to filter text in a pipeline which particularly distinguishes it from other types of editors.

Things to keep in mind

• sed uses special characters differently from the shell so wrap the script part in single quotes
• More info about said can be found on the man page man sed
• Full manual using info sed

  The full documentation for sed is maintained as a Texinfo manual. If the info and sed programs
  are properly installed at your site, the command
  
  info sed
  
  should give you access to the complete manual.

Examples

Simple word replace

• -i - Says to edit the file instead of sending output to stdout
• s - At start is for substitution
• g - At end says to replace all not just first per line
• If both -i and source_file.txt are left out it will read the “file” from stdin and output to stdout

sed -i 's/original_word/replacement_word/g' source_file.txt