codecademy-command line_filesystem
$:shell prompt (命令提示符)
- In the terminal, first you see
$
. This is called a shell prompt. It appears when the terminal is ready to accept a command. - When you type
ls
, the command line looks at the folder you are in, and then "lists" the files and folders inside it. The directories 2014, 2015, and the file hardware.txt are the contents of the current directory $ pwd
/home/ccuser/workspace/blogpwd
stands for "print working directory". It outputs the name of the directory you are currently in, called theworking directory.Here the working directory is blog/. In Codecademy courses, your working directory is usually inside thehome/ccuser/workspace/ directory.
Together with
ls
, thepwd
command is useful to show where you are in the filesystem.$ cd 2015
cd
stands for "change directory". Just as you would click on a folder in Windows Explorer or Finder,cd
switches you into the directory you specify. In other words,cd
changes the working directory.- The directory we change into is
2015
. When a file, directory or program is passed into a command, it is called an argument. Here the 2015 directory is an argument for thecd
comman$ cd jan/memory
To navigate directly to a directory, use
cd
with the directory's path as an argument. Here,cd jan/memory/
command navigates directly to the jan/memorydirectory.$ cd ..
To move up one directory, use
cd ..
. Here,cd ..
navigates up from jan/memory/ to jan/. $ mkdir media
The
mkdir
command stands for "make directory". It takes in a directory name as an argument, and then creates a new directory in the current working directory.Here we used
mkdir
to create a new directory namedmedia/ inside the feb/ directory.touch keyboard.txt
The
touch
command creates a new file inside the working directory. It takes in a filename as an argument, and then creates an empty file in the current working directory.Here we used
touch
to create a new file namedkeyboard.txt inside the 2014/dec/ directory.Congratulations! You've learned five commands commonly used to navigate the filesystem from the command line. What can we generalize so far?
- The command line is a text interface for the computer's operating system. To access the command line, we use the terminal.
- A filesystem organizes a computer's files and directories into a tree structure. It starts with theroot directory. Each parent directory can contain more child directories and files.
- From the command line, you can navigate through files and folders on your computer:
pwd
outputs the name of the current working directory.ls
lists all files and directories in the working directory.cd
switches you into the directory you specify.mkdir
creates a new directory in the working directory.touch
creates a new file inside the working directory.$ ls -a
. .. .preferences action drama comedy genres.xt- The
ls
command lists all files and directories in the working directory. - The
-a
modifies the behavior of thels
command to also list the files and directories starting with a dot (.
). Files started with a dot are hidden, and don't appear when usingls
alone.
The
-a
is called an option. Options modify the behavior of commands. Here we usedls -a
to display the contents of the working directory in more detail.In addition to
-a
, thels
command has several more options. Here are three common options:-a
- lists all contents, including hidden files and directories-l
- lists all contents of a directory in long format-t
- order files and directories by the time they were last modified.$ ls -l
drwxr-xr-x 5 cc eng 4096 Jun 24 16:51 action
drwxr-xr-x 4 cc eng 4096 Jun 24 16:51 comedy
drwxr-xr-x 6 cc eng 4096 Jun 24 16:51 drama
-rw-r--r-- 1 cc eng 0 Jun 24 16:51 genres.txtThe
-l
option lists files and directories as a table. Here there are four rows, with seven columns separated by spaces. Here's what each column means:- Access rights. These are actions that are permitted on a file or directory.
- Number of hard links. This number counts the number of child directories and files. This number includes the parent directory link (
..
) and current directory link (.
). - The username of the file's owner. Here the username is
cc
. - The name of the group that owns the file. Here the group name is
eng
. - The size of the file in bytes.
- The date & time that the file was last modified.
- The name of the file or directory.
$ ls -alt
drwxr-xr-x 4 cc eng 4096 Jun 29 12:22 .
-rw-r--r-- 1 cc eng 0 Jun 29 12:22 .gitignore
drwxr-xr-x 5 cc eng 4096 Jun 30 14:20 ..
drwxr-xr-x 2 cc eng 4096 Jun 29 12:22 satire
drwxr-xr-x 2 cc eng 4096 Jun 29 12:22 slapstick
-rw-r--r-- 1 cc eng 14 Jun 29 12:22 the-office.txtThe
-t
option orders files and directories by the time they were last modified.In addition to using each option separately, like
ls -a
orls -l
, multiple options can be used together, likels -alt
.Here,
ls -alt
lists all contents, including hidden files and directories, in long format, ordered by the date and time they were last modified.cp frida.txt lincoln.txt
The
cp
command copies files or directories. Here, we copy the contents of frida.txt into lincoln.txt.cp biopic/cleopatra.txt historical/
To copy a file into a directory, use
cp
with the source file as the first argument and the destination directory as the second argument. Here, we copy the filebiopic/cleopatra.txt and place it in the historical/directory.cp biopic/ray.txt biopic/notorious.txt historical/
To copy multiple files into a directory, use
cp
with a list of source files as the first arguments, and the destination directory as the last argument. Here, we copy the files biopic/ray.txt and biopic/notorious.txtinto the historical/ directory.cp * satire/
In addition to using filenames as arguments, we can use special characters like
*
to select groups of files. These special characters are called wildcards. The*
selects all files in the working directory, so here we usecp
to copy all files into the satire/ directory.cp m*.txt scifi/
Here,
m*.txt
selects all files in the working directory starting with "m" and ending with ".txt", and copies them to scifi/.The
mv
command moves files. It's similar tocp
in its usage.mv superman.txt superhero/
To move a file into a directory, use
mv
with the source file as the first argument and the destination directory as the second argument. Here we move superman.txtinto superhero/.mv wonderwoman.txt batman.txt superhero/
To move multiple files into a directory, use
mv
with a list of source files as the first arguments, and the destination directory as the last argument. Here, we move wonderwoman.txt and batman.txt intosuperhero/.mv batman.txt spiderman.txt
rm waterboy.txt
The
rm
command deletes files and directories. Here we remove the file waterboy.txt from the filesystem.rm -r comedy
The
-r
is an option that modifies the behavior of therm
command. The-r
stands for "recursive," and it's used to delete a directory and all of its child directories.Be careful when you use
rm
! It deletes files and directories permanently. There isn't an undelete command, so once you delete a file or directory withrm
, it's gone.Congratulations! You learned how to use the command line to view and manipulate the filesystem. What can we generalize so far?
- Options modify the behavior of commands:
ls -a
lists all contents of a directory, including hidden files and directoriesls -l
lists all contents in long formatls -t
orders files and directories by the time they were last modified- Multiple options can be used together, like
ls -alt
- From the command line, you can also copy, move, and remove files and directories:
cp
copies filesmv
moves and renames filesrm
removes filesrm -r
removes directories
- Wildcards are useful for selecting groups of files and directories
- Options modify the behavior of commands:
- The
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