cat
From NetBSD Wiki
The cat(1) utility reads files sequentially, writing them to the standard output. The file operands are processed in command line order. A single dash represents the standard input, and may appear multiple times in the file list.
The word concatenate is just a verbose synonym for catenate.
To write in a file:
$ cat > test An example file.
To append a file:
$ cat newfile >> test
To show the content of a file:
$ cat test An example file.
To concatenate files:
$ cat file1 file2 > newfile
Mini Editing:
$ cat file <<EOF>> text in the file EOF
Or the same with redirection:
$ cat > file text in the file^D
^D means Control+D (end of line)
