Flow

Sed Command Syntax

sed [options] {sed-commands} {input-file}

-f to combine multiple sed-commands ina file and call the sed script file

sed [options] -f {sed-commands-in-a-file} {input-file}

-e to execute multiple sed commands in command line.

sed [options] -e {sed-command-1} -e {sed-command-2} {input-file}

Execute multiple sed commands in command line using {}

sed [options] '{
sed-command-1
sed-command-2
}' {input-file}

Sed never modifies the original file. Use > to redirect output to a file at the end.

Print Pattern Space (p command)

p command prints the current pattern space to stdout.

sed -n 'p' /etc/passwd

-n to silent output for the read line in each cycle. Without this, every line will be output twice.

Print only the 2nd line:

sed -n '2 p' employee.txt

,: Print line 1 through line 4:

sed -n '1,4 p' employee.txt

$: represents the last line:

sed -n '4,$ p' employee.txt

+: used in conjunction with the comma, to specify a number of lines instead of an absolute line number.

sed -n '1,+3' emplyee.txt

~: step

sed -n '1~2 p' emplyee.txt # => print line 1, 3, 5, 7...

Pattern Matching

Print lines matching the pattern "Jane":

sed -n '/Jane/ p' employee.txt

Print lines starting from the 1st match of "Jason" UNTIL the 4th line:

$ sed -n '/Jason/,4 p' employee.txt
102,Jason Smith,IT Manager
103,Raj Reddy,Sysadmin
14,Anand Ram,Developer

If there were no matches for "Jason" in the 1st 4 lines, this command would print the lines that match "Jason" after the 4th line.

Print lines starting from the line matching "Raj" until the line matching "Jane"

sed -n '/Raj/,/Jane/ p' employee.txt

Delete Lines (d command)

Conceptional similar to p command, pattern matching then DON'T output the matching line(s)

Delete all the empty lines from a file:

sed '/^$/ d' employee.txt

Delete all comment lines(assuming the comment starts with #)

sed '/^#/ d' employee.txt

Write Pattern Spae to File (w command)

Write the content of employee.txt file to file output.txt (and display on screen, -n option can disable the screen printing).

sed 'w output.txt' employee.txt

With pattern matching:

sed '1,4 w output.txt' employee.txt

> can be a replacement of this w command