topic Re: copying file content to memory in Operating System - Linux

copying file content to memory

Piotr Kirklewski — Sat, 18 Dec 2010 00:26:26 GMT

Hi there
How can I copy a text-file content to the memory without editing the file ?
For example there is 12000 lines of text in file "A" and I want to copy and paste all of it to file "B" between line 1 and 3 ?
Is there any way of doing that without manually copying all the 12000 lines ?

Re: copying file content to memory

Steven Schweda — Sat, 18 Dec 2010 03:54:49 GMT

> How can I copy a text-file content to the
> memory without editing the file ?

By "to the memory", do you mean "to another
file"?

> [...] between line 1 and 3 ?

What did you want to do with line 2, which is
currently between lines 1 and 3?

> Is there any way of doing that [...]

Depending on exactly what "that" is, there
are probably several ways. Here's a crude
way of doing something:

man cat
man sed

M=2
N=3
( sed -n -e "1,${M}p" A ; cat B ; sed -n -e "${N},\$p" A )

For example:

alp$ cat A
File A line 1.
File A line 2.
File A line 3.
File A line 4.

alp$ cat B
File B line 1.
File B line 2.
File B line 3.
File B line 4.

alp$ sed -n -e "1,${M}p" A
File A line 1.
File A line 2.

alp$ sed -n -e "${N},\$p" A
File A line 3.
File A line 4.

alp$ ( sed -n -e "1,${M}p" A ; cat B ; sed -n -e "${N},\$p" A )
File A line 1.
File A line 2.
File B line 1.
File B line 2.
File B line 3.
File B line 4.
File A line 3.
File A line 4.

Re: copying file content to memory

dirk dierickx — Tue, 21 Dec 2010 07:55:37 GMT

what about just using plain old head/tail commands?

head -2 file_a | tail -n 1 >> file_b

Re: copying file content to memory

Steven Schweda — Tue, 21 Dec 2010 13:04:57 GMT

> what about just using plain old head/tail
> commands?

Did you try your suggestion before posting
it? How well did it work for you?

Plain old "head" and "tail" commands can
extract parts of one file, but it may not be
immediately clear how you assemble the
pieces. (Even if you do get the right
pieces.)

And, of course, I seem to have reversed the
roles of "A" and "B" in my example, if I
understand the original question (which I
don't claim to do).