Creating and moving files

So far you have looked at files without changing anything. Now you start changing things: making directories for a project, copying a config file before you edit it, renaming a log, cleaning up old files. These commands are short and fast, and Linux does not ask "are you sure" by default. There is no bin to restore from.

By the end you can create files and directories, copy, move, rename and delete them, and use the habits that stop you deleting the wrong thing.

Making files and directories

touch creates an empty file. If the file exists, it leaves the contents alone and updates its modified time to now:

$ touch notes.txt
$ ls -l notes.txt
-rw-r--r-- 1 root root 0 Oct 24 11:18 notes.txt

You will more often create a file by writing into it with >, as in the first topic, or with an editor, which the Editing files topic covers.

mkdir (make directory) creates a directory:

$ mkdir reports

It fails if the directory already exists, or if a parent along the path is missing:

$ mkdir reports
mkdir: cannot create directory 'reports': File exists
$ mkdir a/b/c
mkdir: cannot create directory 'a/b/c': No such file or directory

-p (parents) creates every missing directory along the path, and does not complain if they already exist. That makes it safe to run twice, which is why scripts nearly always use it:

$ mkdir -p a/b/c
$ mkdir -p a/b/c

Copying with cp

cp copies a file. The first argument is the source, the last is the destination:

$ cp app.conf app.conf.bak
$ ls
app.conf  app.conf.bak  notes.txt  reports

If the destination is an existing directory, the copy goes inside it and keeps its name. You can copy several files into a directory in one go:

$ cp app.conf app.conf.bak reports/
$ ls reports
app.conf  app.conf.bak

cp skips directories unless you add -r (recursive), which copies the directory and everything inside it:

$ cp reports reports-old
cp: -r not specified; omitting directory 'reports'
$ cp -r reports reports-old
$ ls reports-old
app.conf  app.conf.bak

Watch what happens when you run the same cp -r again. reports-old now exists, so the second copy goes inside it, as reports-old/reports. Check with ls after copying directories.

Copying a config file before you change it is a habit worth having. If your edit breaks the service, you copy the old version back.

Moving and renaming with mv

mv (move) works like cp, except the original is gone afterwards. Linux has no separate rename command: renaming is moving a file to a new name in the same directory.

$ mv notes.txt todo.txt
$ mv todo.txt reports/
$ ls reports
app.conf  app.conf.bak  todo.txt

mv moves directories without needing -r:

$ mv reports-old archive

There is one trap. If the destination is not an existing directory, mv treats it as a new name. If you mean to move app.conf into a directory called backup and that directory does not exist, the file is renamed to backup instead:

$ mv app.conf backup
$ ls -l backup
-rw-r--r-- 1 root root 10 Oct 24 11:18 backup

Put a / after a name you mean as a directory. Then mv and cp stop with an error if it is not one:

$ mv app.conf backup/
mv: cannot move 'app.conf' to 'backup/': Not a directory

Overwriting without warning

cp and mv replace an existing destination file without asking. This copy silently wipes out whatever was in app.conf:

$ cp app.conf.bak app.conf

Three options help:

$ cp -i app.conf.bak app.conf
cp: overwrite 'app.conf'? n
$ cp -v app.conf.bak app.conf
'app.conf.bak' -> 'app.conf'

-v is useful in scripts and when you work with patterns, so you can see exactly which files were touched.

Deleting with rm and rmdir

rm (remove) deletes files. There is no undo. The file is not moved anywhere; it is gone.

$ rm reports/todo.txt

rm refuses to delete a directory on its own. rmdir deletes a directory only if it is empty, which makes it a safe choice. To delete a directory and everything inside it, use rm -r:

$ rm archive
rm: cannot remove 'archive': Is a directory
$ rmdir archive
rmdir: failed to remove 'archive': Directory not empty
$ rm -r archive

You will see rm -rf in many guides. -f (force) means do not ask and do not complain about missing files. Together they delete a whole tree without a single question. Used on the wrong path, on a server, as root, this is how people lose data. Read every rm -r twice before you press Enter, and use an absolute path when you are not sure where you are.

Spaces in names matter even more here. rm my notes.txt tries to delete two files, my and notes.txt. If both existed, both would be gone:

$ rm my notes.txt
rm: cannot remove 'my': No such file or directory
rm: cannot remove 'notes.txt': No such file or directory
$ rm "my notes.txt"

Working with many files at once

The * pattern from the Looking at files topic works with all of these commands. rm *.log deletes every file ending in .log in the current directory.

Because the shell expands the pattern before the command runs, you can check it first. Run ls with the same pattern, read the list, then swap ls for rm:

$ ls *.log
a.log  b.log
$ rm -v *.log
removed 'a.log'
removed 'b.log'

A stray space is the classic disaster: rm * .log with a space deletes everything in the directory, then complains that .log does not exist. Listing first catches it. rm -i asks about each file, which is slow, but sensible when you are unsure.

Tasks

Do these in your Linux shell.

Task 1: Tidy a directory

Create a messy directory:

$ mkdir -p ~/tidy && cd ~/tidy
$ touch app.log worker.log db.conf app.conf readme.txt

Now, from inside ~/tidy:

1. Create directories logs and config.
2. Move both .log files into logs with one command.
3. Copy both .conf files into config, so the originals stay where they are.
4. Rename readme.txt to README.

Check the result with ls -R, which lists subdirectories too.

$ mkdir logs config
$ mv *.log logs/
$ cp *.conf config/
$ mv readme.txt README
$ ls -R
.:
README  app.conf  config  db.conf  logs

./config:
app.conf  db.conf

./logs:
app.log  worker.log

Task 2: Clean up safely

Still in ~/tidy:

1. Delete the two .conf files at the top level, but not the copies in config. List them first.
2. Try to remove the logs directory with rmdir, and read the error.
3. Remove logs and its contents.

$ ls *.conf
app.conf  db.conf
$ rm -v *.conf
removed 'app.conf'
removed 'db.conf'
$ rmdir logs
rmdir: failed to remove 'logs': Directory not empty
$ rm -r logs
$ ls -R
.:
README  config

./config:
app.conf  db.conf

Quiz

1. You run cp -r site backup twice. What do you end up with?

2. You are on a server about to change /etc/app/app.conf. What do you run first, and why?

3. What is the difference between rmdir old and rm -r old?

4. You meant to type rm *.tmp but typed rm * .tmp. What happens, and how would you have caught it?