How to insert a line using sed before a pattern and after a line number?

Question

How to insert a line into a file using sed before a pattern and after a line number? And how to use the same in shell script?

This inserts a line before

Answer 1

Simple? From line 12 to the end:

sed '12,$ s/.*Sysadmin.*/Linux Scripting\n&/' filename.txt

Answer 2

You can either write a sed script file and use:

sed -f sed.script file1 ...

Or you can use (multiple) -e 'command' options:

sed -e '/SysAdmin/i\
Linux Scripting' -e '1,$s/A/a/' file1 ...

If you want to append something after a line, then:

sed -e '234a\
Text to insert after line 234' file1 ...

Answer 3

I assume you want to insert the line before a pattern only if the current line number is greater than some value (i.e. if the pattern occurs before the line number, do nothing)

If you're not tied to sed:

awk -v lineno=$line -v patt="$pattern" -v text="$line_to_insert" '
    NR > lineno && $0 ~ patt {print text}
    {print}
' input > output

Answer 4

here is an example of how to insert a line before a line in a file:

example file test.txt :

hello line 1
hello line 2
hello line 3

script:

sed -n 'H;${x;s/^\n//;s/hello line 2/hello new line\n&/;p;}' test.txt > test.txt.2

output file test.txt.2

hello line 1
hello new line
hello line 2
hello line 3

NB! notice that the sed has as beginning a substitution of a newline to no space - this is necessary otherwise resulting file will have one empty line in the beginning

The script finds the line containing "hello line 2", it then inserts a new line above -- "hello new line"

explanation of sed commands:

sed -n:
suppress automatic printing of pattern space

H;${x;s/test/next/;p}

/<pattern>/  search for a <pattern>
${}  do this 'block' of code
H    put the pattern match in the hold space
s/   substitute test for next everywhere in the space
x    swap the hold with the pattern space
p    Print the current pattern hold space.