🐴 Sed

 1sed -e '…' -e '…'  # Several execution 
 2sed -i             # Replace in place 
 3sed -r             # Play with REGEX
 4
 5# The most usefull
 6sed -e '/^[ ]*#/d' -e '/^$/d' <fich.>    #   openfile without empty or commented lines
 7sed 's/ -/\n -/g'                        #   replace all "-" with new lines
 8sed 's/my_match.*/ /g'                   #   remove from the match till end of line
 9sed -i '4048d;3375d' ~/.ssh/known_hosts  #   delete lines Number
10
11# Buffer 
12s/.*@(.*)/$1/;                                        #  keep what is after @ put it in buffer ( ) and reuse it with $1.
13sed -e '/^;/! s/.*-reserv.*/; Reserved: &/' file.txt  #  resuse search with &
14
15# Search a line
16sed -e '/192.168.130/ s/^/#/g' -i /etc/hosts          # Comment a line 
17sed -re 's/^;(r|R)eserved:/; Reserved:/g' file.txt    # Search several string
18
19# Insert - add two lines below a match pattern
20sed -i '/.*\"description\".*/s/$/ \n  \"after\" : \"network.target\"\,\n  \"requires\" : \"network.target\"\,/g'  my_File  
21
22# Append
23sed '/WORD/ a Add this line after every line with WORD'
24
25# if no occurence, then add it after "use_authtok" 
26sed -e '/remember=10/!s/use_authtok/& remember=10/' -i /etc/pam.d/system-auth-permanent