mjhjmtu

I have two files: file_a and file_b. I want to redirect (>) all content of file_a into file_b.

pseudo code is file_a > file_b. how to do that? I feel I should use cat.

Nitpick: In Unix, you can redirect output or input streams, but you can't redirect files.

As RomanPerekhrest suggested in comments to the question:

cat file_a >file_b

This redirects the standard output stream (or just "the output") of cat into file_b. The output of cat will be the contents of file_a.

This has the same effect (disregarding edge-case differences regarding permissions and ownership) as

cp file_a file_b

There are many other ways of duplicating a file's complete contents into another file, including trivial examples that apply non-modifying filters on text files, such as

dd if=file_a of=file_b

awk '1' file_a >file_b

sed '' file_a >file_b

etc.

All the above examples will overwrite the previous contents of file_b.

To append to file_b, replace > in the examples above that uses > with >>, e.g.

cat file_a >>file_b

To append the contents of file_a to that of file_b and store that in a third file:

cat file_b file_a >file_c

cat will output the contents of each of its file arguments after each other, in order, and the result will be redirected into the new file_c file.

simple way is to copy:

cp file1 file2

there are multiple ways to divert the flow of output data into another file as well e.g.:

cat file1 > file2
less file1 > file2
more file1 > file2

You can use rsync to take backup:

rsync -r /media/hdd1/Folder1/ /media/hdd2/Folder2/

rsync is backing up whole folder from one drive to another and -r option specifies to do it recursively for all files and subfolders.