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File Operation

Once we arrive the working directory, the next thing we want to do might be manipulating files: copying, renaming, deleting and so forth. This page introduces a few things that can be useful in handling files in a Linux system.

The content on this page mostly comes from Linux pocket guide by Daniel J. Barrett.

ls [options] [files]

The ls command lists attributes of files and directories. You can list files in the current directory:

$ ls

in a given directories:

$ ls dir1 dir2 dir3

or individually:

$ ls file1 file2 file3

The most important options are -a and -l. By default, ls hides files whose names begin with a dot. The option -a displays all files including those starting with .(dot). The -l option produces a long listing, for example:

-rw-r--r--  1 hajsong  staff  3376 Sep  3 08:18 _index.md
-rw-r--r--  1 hajsong  staff  1340 Sep  3 12:53 configuration.md
-rw-r--r--  1 hajsong  staff  3301 Sep  3 13:05 fileoperation.md
-rw-r--r--  1 hajsong  staff  2707 Sep  3 12:52 filesystem.md
-rw-r--r--  1 hajsong  staff  1066 Sep  3 11:23 shell.md

that includes, from left to right: the file’s permissions, owner, group, size, last modification date and name. When using the -l option, the list is created in the alphabetical order of the file names. It is sometimes useful to find out the most recently modified file. In this case, you can change the order according to the modification times.

$ ls -ltr

The result looks like:

-rw-r--r--  1 hajsong  staff  3376 Sep  3 08:18 _index.md
-rw-r--r--  1 hajsong  staff  1066 Sep  3 11:23 shell.md
-rw-r--r--  1 hajsong  staff  2707 Sep  3 12:52 filesystem.md
-rw-r--r--  1 hajsong  staff  1340 Sep  3 12:53 configuration.md
-rw-r--r--  1 hajsong  staff  3787 Sep  3 13:08 fileoperation.md

Here, -t makes the order according to the modification time, and -r reverses the order so that the latest comes to the bottom of the list. You may already notice that you can combine options by just line them up.

cp [options] [files] (file/dir)

The cp command copies a file:

$ cp file file2

Using the -R option, you can also recursively copy directories.

$ cp -R dir1 dir2

will create dir2 which is the same as dir1.

Useful options

ln [options] source target

A link is a reference to another file, created by the ln command. There are two kinds of links. A symbolic link refers to another file by its path, much like a Windows “shortcut” or a Mac “alias”.

$ ln -s myfile softlink

If you delete the original file, the now-dangling link will be invalid, pointing to a nonexistent file path. A hard link, on the other hand, is simply a second name for a physical file on disk. Deleting the original file does not invalidate the link.

If you leave the softlink blank, then you get the link with the same name.

$ ln myfile hardlink

Symbolic link can cross disk partitions, since they are just references to file paths. Hard links cannot. Symbolic links can also point to directories, whereas hard links cannot.

It is easy to find out where a symbolic link points with either of these command.

$ readlink softlink

or

$ ls -l softlink

useful options

mv [options] source target

The mv command can rename a file:

$ mv file1 file2

or move files and directories into a destination directory.

$ mv file1 destination_directory

useful options

rm [options] files/directories

The rm command can delete files:

$ rm file1 file2 file3

or recursively delete directories:

rm -r dir1 dir2

useful options