Sed
Sed tricks
To remove the line and print the output to standard out:
sed '/pattern to match/d' ./infile
To directly modify the file:
sed -i '/pattern to match/d' ./infile
To directly modify the file (and create a backup):
sed -i.bak '/pattern to match/d' ./infile
Delete N lines in a file
As long as the file is not a symlink or hardlink, you can use sed, tail, or awk. Example below.
$ cat t.txt
12
34
56
78
90
$ sed -e '1,3d' < t.txt
78
90
Delete empty lines
sed '/^\s*$/d'
sed + remove # and empty lines with one sed command
sed -e 's/#.*$//' -e '/^$/d' inputFile
Remove trailing witespaces
sed -i 's/[ \t]*$//' file
Replace between strings
sed -n -e '/Word A/,/Word D/ p' file
Remove carriage return and merge lines
# exemple to remove 'server_alias' from line 2 and merge it with line 1:
sed -e ':a' -e 'N' -e '$!ba' -e 's/\;\n server_alias//g' -i file
Insert new line at top of file
# 1i is important, the leading \ pushes the content at line 2
sed -i -e '1i# {{ ansible_managed }}\' $file
Replace new lines by spaces
sed ':a;N;$!ba;s/\n/ /g' $file