Linux: GNU and Unix Commands - dummies

By Emmett Dulaney

The Linux+ certification exam from CompTIA covers the topic of GNU and Unix commands. The table shows the subtopics, weights, descriptions, and key knowledge areas for this topic.

Breakout of Domain 103
Subtopic Weight Description Key Areas
Work on the command line 4 Interact with shells and commands using the command line and
the bash shell
Use single shell commands and one-line command sequences as
well as modify the shell environment and use/edit command
Process text streams using filters 3 Apply filters to text streams Send text files and output streams through text utility
Perform basic file management 4 Use the basic Linux commands to manage files and
Copy, move, and delete files and directories individually and
Use streams, pipes, and redirects 4 Redirect streams and connect them – including standard
output, standard input, and standard error
Pipe the output of one command to the input of another
Create, monitor, and kill processes 4 Perform basic process management Run jobs in the foreground and background; send signals to
Modify process execution priorities 2 Manage process execution priorities Run programs with higher and lower priorities than the
Search text files using regular expressions 2 Understand regular expressions and how to use them Create simple regular expressions and perform searches
Perform basic file editing operations using vi 3 Understand vi navigation, editing,
copying, deleting, etc.
Use basic vi modes to insert, edit,
copy, delete, and find text.

To adequately address these topics, focus on the following files, terms, and utilities: &, ., bash, bg, bzip2, cat, cp, cpio, cut, dd, echo, egrep, env, exec, expand, export, fg, fgrep, file, file globbing, find, fmt, free, grep, gunzip, gzip, head, history, jobs, join, kill, killall, ls, man, mkdir, mv, nice, nl, nohup, od, paste, pr, ps, pwd, regex(7), renice, rm, rmdir, sed, set, sort, split, tail, tar, tee, top, touch, tr, uname, unexpand, uniq, unset, uptime, vi, wc, and xargs.

Here are the top ten items to know as you study for this domain:

  1. When run, every command spans at least one process and processes can be viewed with ps or top (which continues to update the display dynamically).

  2. Jobs can run in the foreground or background and be moved between the two. Jobs running in the foreground can be suspended by pressing Ctrl+Z.

  3. Files can be copied using cp or moved using mv. Files can be deleted with rm and directories (which are created with mkdir) can be removed with rmdir. Recursive deletion can be done with rm –r.

  4. To change directories, use the cd command. When used without parameters, this will move you to your home directory. To see what directory you are presently working in, use the pwd (present working directory) command.

  5. The ls command has a plethora of options to allow you to list files. The –a option will list all (including hidden) files.

  6. The cut command can pull fields from a file and they can be combined using either paste or join. The latter offers more features than the former and can be used with conditions.

  7. The wc command can count the number of lines, words, and characters in a file.

  8. The grep utility (and its counterparts egrep and fgrep) can be used to find matches for strings within files.

  9. The find command can be used to search the system for files/directories that meet any number of criteria. When these entities are found, the xargs command can be used to look deeper within them for other values (such as in conjunction with grep).

  10. It’s possible to convert data from one value to another by using a number of utilities. The most popular would include the tr (translate) utility and sed (the stream editor).