Linux regularity

Sed

The format of the sed command is that n within sed-n'nroomp filename single quotation marks is a number or character indicating the number of lines. The-n option shows how many lines we want to print, but irrelevant lines are not displayed.

First create a sed directory to copy the files of passwd to the sed directory and rename it to test.txt

Print out the first line of the test file # sed-n '1roomp test.txt* to remove the-n parameter is to print out all the lines or regular expression printing # sed-n' 1 test.txt* specified interval printing 1 to 3 lines # sed-n'1 test.txt* printing a character # sed-n'/ root/'p test.txt* this usage is similar to grep Special characters used in grep, such as ^ $. * etc.) can also be used in sed using the * print first behavior root (^ represents the first line, printed with root at the beginning) # sed-n'/ ^ root/'p test.txt* prints the last line bash ($represents the last line) # sed-n'/ bash$/'p test.txt* prints a line greater than three o # sed-n'/ ooo*/'p test.txt