This section introduces you to basic commands related to files.
###wc
wc stands for "wordcount". It prints newline-, word-, and byte-counts for each file, and a summary line if more than one FILE is specified.
Syntax:
wc [OPTION]... [FILE]...
###diff
diff stand for "difference", compare files line by line.
Syntax:
diff [OPTION]... [FILE]...
###chown
chown stands for "change owner". It can also change group owner.
Syntax:
chown [OPTION]... [OWNER][:[GROUP]] FILE...
###chmod
chmod stands for "change file mode bits" and controls the following permissions on any given file:
-
Read: Who can see the file data.
-
Write: Who can modify the file.
-
Execute: Who is allowed to run the file (like a program or a script)
Permissions can be read using ls -l.
Syntax:
chmod [OPTION]... MODE[,MODE]... FILE...
###echo
echo - output the given line of text (useful for displaying the content of variables)
Syntax:
echo [SHORT-OPTION]... [STRING]...
###touch
touch - change file timestamps (access and modification times) to the current time or to a specific one defined through the options.
Most useful for creating new, empty files.
Syntax:
touch [OPTION]... FILE...
-t STAMP` use [[CC]YY]MMDDhhmm[.ss] instead of current time
Note: a FILE argument that does not exist is created empty (this mode of operation was already used in the section basics).
###ln
ln - make links between files.
Syntax to create a link to TARGET with the name LINK_NAME:
ln [OPTION]... [-T] TARGET LINK_NAME
Note: If you use ln like this, it will create a so-called 'hardlink'. It is generally advisable to use softlinks (symlinks) instead, because they will also work across file systems. To do so, you will need to pass the -s flag like this: ln -s TARGET LINK_NAME. Be aware that you will have to use the absolute path for TARGET.
###file
file - determine file type.
Syntax:
file [OPTION]... FILE...
###less
less - A file viewer.
less allows to scroll forward and backward in a file with the arrow keys. The current file can be opened in an editor by pressing v, and less can be quit by pressing q.
Syntax:
less [OPTION]... [filename]...
###which (whereis)
which - shows the full path of (shell) commands.
Syntax:
which [options] [--] programname [...]
whereis - locate the binary, source, and manual page files for a command.
Syntax:
whereis [OPTIONS] name...
###Exercise 1
a) For this set of exercises, create the temporary working directory TempDir in your home directory. Now, make it your current working directory.
b) Create the file capture.txt containing some text typed through your keyboard.
Hint: Use a console text editor such as nano
c) How many lines, words and characters does this file have?
d) Make a copy of the file and compare both files.
e) Append text to the copied file and compare with the original.
f) Assign user root and group users as new owner of the original file and check the change.
Hint: Check the current owners of the files first
g) Change the file attributes to make it write protected and try to append text again.
h) Generate a new line in the terminal which contains "Hello World!".
i) Change the date and time of the file capture.txt to 31.01.2017 00:01 and check the result.
j) Create a link to the capture.txt file in the desktop, minimize the terminal and look for the new link on the desktop. Can the text editor open the file?
k) Check the file types in the following directories: your test directory, downloads, pictures and music. Make a list of all those file types creating the file-types.log file.
l) Explore the log file file-types.log with the command less.
m) Obtain the location of the command ls, as well as the location of it's manual.
n) Delete the content of TempDir directory and check it was deleted. Then delete the directory.