'What is the difference between p and P in sed?
Can anyone explain what is the difference between p
and P
in Sed?
Suppose I want to print lines containing gmail in the below file using both p
and P
give the same output:
$ cat abc.txt
Gmail 10
Yahoo 20
Rediff 18
$ sed -n /Gmail/p abc.txt
Gmail 10
$ sed -n /Gmail/P abc.txt
Gmail 10
What is the difference between p
and P
?
Solution 1:[1]
In sed, p
prints the addressed line(s), while P
prints only the first part (up to a newline character \n
) of the addressed line. If you have only one line in the buffer, p
and P
are the same thing, but logically p
should be used.
Let's look at an academic but easy example. Let's assume we want to print line number 1, we can do
$ echo "line 1
$ This is line 2" | sed -n '1p'
> line 1
We could also do
$ echo "line 1
$ This is line 2" | sed -n '1P'
> line 1
Both commands do the same thing, since there is no newline character in the buffer.
But now we use the N
command to add a second line into the buffer:
$ echo "line 1
$ This is line 2" | sed -n '1{N; p}'
> line 1
> This is line 2
Now we had 2 lines in the buffer and we print them both with p
.
$ echo "line 1
$ This is line 2" | sed -n '1{N; P}'
> line 1
Again we had 2 lines in the buffer, but we printed only the first one, since we were using P
and not p
.
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
Solution | Source |
---|---|
Solution 1 |