We can use the sed stream editor provided by linux to filter
and convert text line by line.
Options for sed command
Here are some options for sed commands.
Options
Option
Meaning
-n or ‑‑quiet or ‑‑silent
Ignore the automatic output.
-e script or ‑‑expression=script
Add the script.
-f script-file or ‑‑file=script-file
Add the script-file’s content.
-r or ‑‑regexp-extended
Use extended regular expressions.
Commands
Zero- or One- address commands
Command
Meaning
a \text
Append text after the specified lines.
i \text
Insert text before the specified lines.
r filename
Append text from filename.
Commands with accept address ranges
Command
Meaning
c \
d
Delete matching lines.
p
Output matching lines.
s/regexp/replacement/
Replace the content that the regexp matches with the
content of the replacement, append g at the end means
match globally, append i at the end means to ignore
case.
w filename
Write the specified content to filename.
Addresses
Address
Meaning
number
Match the specified line number.
first~step
Match every step line starting with line first.
$
Match the last line.
/regexp/
Output lines matching the regular expression.
addr1,addr2
Output the contents from lines addr1 to addr2.
addr1,-N
Output the contents from lines addr1 to N lines.
Examples
Before we get started, let’s prepare some test content:
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printf'%s\n'\
'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam nisi tellus,'\
'egestas sed dolor nec, eleifend venenatis mi. Mauris ac ligula'\
'scelerisque libero interdum varius. Aenean nec arcu nec turpis'\
'commodo mollis. Morbi suscipit felis libero, eu sollicitudin justo'\
'condimentum id. Praesent eu metus rutrum, varius leo malesuada,'\
'varius sapien. Vestibulum blandit, dolor bibendum bibendum ultricies,'\
'ipsum velit pretium arcu, eu maximus augue massa vitae justo. Etiam'\
'elit sapien, placerat quis libero a, tincidunt ornare erat. Praesent eu nibh'\
'ac sem mattis tincidunt. Aliquam erat volutpat. Nulla egestas dui ac urna'\
'convallis, vel egestas lectus ultrices. Morbi sit amet quam eget tortor'\
'laoreet laoreet id non libero.' > sed_file
Match From Line One to Line Five
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sed -n '1,5p' sed_file
Match The Last Line
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sed -n '$p' sed_file
Append Lines After Line One, Two and Three
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sed '1,3a \A Line After Line One, Two and Three' sed_file
