4.3.2 Basic Unix commands

Let's learn the basic Unix commands. [ 20] Try all the following commands from the non-privileged user account penguin :

• pwd

  • Display name of current/working directory.

• whoami

  • Display current user name.

• file foo

  • Display a type of file for the file foo.

• type -p commandname

  • Display a file location of command commandname.

  • which commandname does the same. [21]

• type commandname

  • Display information on command commandname.

• apropos key-word

  • Find commands related to key-word.

  • man -k key-word does the same.

• whatis commandname

  • Display one line explanation on command commandname.

• man -a commandname

  • Display explanation on command commandname. (Unix style)

• info commandname

  • Display rather long explanation on command commandname. (GNU style)

• ls

  • List contents of directory. (non-dot files and directories) [22]

• ls -a

  • List contents of directory. (all files and directories)

• ls -A

  • List contents of directory. (almost all files and directories, i.e., skip ".." and ".")

• ls -la

  • List all contents of directory with detail information. See The filesystem concept in Debian, Section 4.5.2.

• ls -d

  • List all directories under the current directory.

• lsof foo

  • List open status of file foo.

• mkdir foo

  • Make a new directory foo in the current directory.

• rmdir foo

  • Remove a directory foo in the current directory.

• cd foo

  • Change directory to the directory foo in the current directory or in the directory listed in the variable CDPATH. See cd command in builtins(7).

• cd /

  • Change directory to the root directory.

• cd

  • Change directory to the current user's home directory.

• cd /foo

  • Change directory to the absolute path directory /foo.

• cd ..

  • Change directory to the parent directory.

• cd ~foo

  • Change directory to the home directory of the user foo.

• cd -

  • Change directory to the previous directory.

• </etc/motd pager

  • Display contents of /etc/motd using the default pager. See command < foo, Section 4.3.10.9. [ 23]

• touch junkfile

  • Create a empty file junkfile.

• cp foo bar

  • Copy a existing file foo to a new file bar.

• rm junkfile

  • Remove a file junkfile.

• mv foo bar

  • Rename an existing file foo to a new name bar.

• mv foo bar/baz

  • Move an existing file foo to a new location with a new name bar/baz. The directory bar must exist.

• chmod 600 foo

  • Make an existing file foo to be non-readable and non-writable by the other people. (non-executable for all)

• chmod 644 foo

  • Make an existing file foo to be readable but non-writable by the other people. (non-executable for all)

• chmod 755 foo

  • Make an existing file foo to be readable but non-writable by the other people. (executable for all)

• top

  • Display process information using full screen. Type "q" to quit.

• ps aux | pager

  • Display information on all the running processes using BSD style output. See command1 | command2, Section 4.3.10.2.

• ps -ef | pager

  • Display information on all the running processes using Unix system-V style output.

• ps aux | grep -e "[e]xim4*"

  • Display all processes running exim or exim4. Learn the regular expression from grep(1) manual page by typing man grep. [ 24]

• ps axf | pager

  • Display information on all the running processes with ASCII art output.

• kill 1234

  • Kill a process identified by the process ID: 1234. See Kill a process, Section 8.5.1.

• grep -e "pattern" *.html

  • Find a "pattern" in all of the files ending with .html in current directory and display them all.

• gzip foo

  • Compress foo to create foo.gz using the Lempel-Ziv coding (LZ77).

• gunzip foo.gz

  • Decompress foo.gz to create foo.

• bzip2 foo

  • Compress foo to create foo.bz2 using the Burrows-Wheeler block sorting text compression algorithm, and Huffman coding. (Better compression than gzip)

• bunzip2 foo.bz2

  • Decompress foo.bz2 to create foo.

• tar -xvvf foo.tar

  • Extract files from foo.tar archive.

• tar -xvvzf foo.tar.gz

  • Extract files from gzipped foo.tar.gz archive.

• tar -xvvf --bzip2 foo.tar.bz2

  • Extract files from foo.tar.bz2 archive. [25]

• tar -cvvf foo.tar bar/

  • Archive contents of folder bar/ in foo.tar archive.

• tar -cvvzf foo.tar.gz bar/

  • Archive contents of folder bar/ in compressed foo.tar.gz archive.

• tar -cvvf --bzip2 foo.tar.bz2 bar/

  • Archive contents of folder bar/ in foo.tar.bz2 archive. [ 26]

• zcat README.gz | pager

  • Display contents of compressed README.gz using the default pager.

• zcat README.gz > foo

  • Create a file foo with the decompressed content of README.gz.

• zcat README.gz >> foo

  • Append the decompressed content of README.gz to the end of the file foo. (If it does not exist, create it first.)

• find . -name pattern

  • find matching filenames using shell pattern. (slower)

• locate -d . pattern

  • find matching filenames using shell pattern. (quicker using regularly generated database)

Please traverse directories and peek into the system using above commands as a training. If you have questions on any of the console commands, please make sure to read the manual page. For example, these commands are the good start:

     $ man man
     $ man bash
     $ man ls

Also this is a good timing to start vim and press F1-key. You should at least read the first 35 lines. Then do the online training course by moving cursor to |tutor| and pressing Ctrl-]. See Editors, Chapter 11 to learn more about editors.

Please note that many Unix-like commands including ones from GNU and BSD will display brief help information if you invoke them in one of the following ways (or without any arguments in some cases):

     $ commandname --help
     $ commandname -h

Try also examples in Debian tips, Chapter 8 as your self training.