How do you redirect standard output (stdout) to a file in Linux?

Use > (or the explicit 1>) — ls > files.txt sends normal output to the file instead of the screen.

ls > files.txt      # stdout into files.txt
ls 1> files.txt     # identical — the 1 is just explicit

The bare > defaults to FD 1 (stdout), so > file and 1> file mean exactly the same thing. You almost never write the 1; it only becomes useful for clarity when stderr is also in play.

Watch out — > truncates:

• If the file exists, it is wiped the moment the command starts (even before any output is produced), then rewritten from scratch.
• If it doesn't exist, it's created.
• Nothing appears on screen — the output went into the file.

This "truncate first" behaviour bites people: sort file > file destroys file (the shell empties it before sort ever reads it). To append instead of overwrite, use >>.

Tip: Want to add to a file, not replace it? That's >>, covered separately.