The
Linux operating system makes use of terminal
commands to work with a computer's file system. The primary use
of the Linux command sed,
which is short for stream editor, is to modify each line of a file or stream by
replacing specified parts of the line. It makes basic text changes to a file or
input from a pipeline.
For example, say you have a file named "songs.text"
that contains these lines:
1,
Justin Timberlake, Title 545, Price $6.30
2,
Taylor Swift, Title 723, Price $7.90
3,
Mick Jagger, Title 610, Price $7.90
4,
Lady Gaga, Title 118, Price $6.30
5,
Johnny Cash, Title 482, Price $6.50
6,
Elvis Presley, Title 335, Price $6.30
7,
John Lennon, Title 271, Price $7.90
Making Text Substitutions With Sed
If
you want to change all price occurrences of $6.30 to $7.30, you can make
the changes using the sed command in this way:
sed
's/6.30/7.30/' songs.txt > songs2.txt
This
code makes the change and writes the modified file to "songs2.txt".
The output file contains:
1,
Justin Timberlake, Title 545, Price $7.30
2,
Taylor Swift, Title 723, Price $7.90
3,
Mick Jagger, Title 610, Price $7.90
4,
Lady Gaga, Title 118, Price $7.30
5,
Johnny Cash, Title 482, Price $6.50
6,
Elvis Presley, Title 335, Price $7.30
7,
John Lennon, Title 271, Price $7.90
If
you want to replace all occurrences of "Cash" with
"Trash" you use:
sed
's/Cash/Trash/' songs.txt > songs2.txt
which creates
a file with content:
1,
Justin Timberlake, Title 545, Price $7:30
2,
Taylor Swift, Title 723, Price $7.90
3,
Mick Jagger, Title 610, Price $7.90
4,
Lady Gaga, Title 118, Price $7:30
5,
Johnny Trash, Title 482, Price $6.50
6,
Elvis Presley, Title 335, Price $7:30
7,
John Lennon, Title 271, Price $7.90
Filtering With the Sed Command
Sed
is also frequently used to filter lines in a file or stream. For example, if
you only want to see the lines containing "John," you use:
sed
-n '/John/p' songs.txt > johns.txt
which writes
the following lines to file johns.txt:
5,
Johnny Trash, Title 482, Price $6.50
7,
John Lennon, Title 271, Price $7.90
https://www.lifewire.com/example-uses-of-sed-