$ cat file.txt
line 1
line 2
this is the line
line 4
line 5
If you want lines starting from "this is the line"
$ cat file.txt | awk '/this is the line/{ f=1; } f'
this is the line
line 4
line 5
When the line is found, set f to 1.
The last 'f' is shortcut to 'f == 1 { print }'
If you want output after the matching line
$ cat file.txt | awk '/this is the line/{ f=1; next; } f'
line 4
line 5
