List of Bash online-tutorials¶

Here's a list of some Bash tutorials.

The primary purpose of that list is to lead beginners to good tutorials and not to the wrong ones. However, the secondary purpose is to provide information to increase quality of the linked tutorials.

My experience shows that nobody is interested when you "just send a mail to the author", even if he links a big "contact me" in his article(s). This is another try of influencing the Bash world.

List¶

This is a test for the data plugin. For now, please use the next section.

---- datatable tutorial ---- cols : %pageid%, recindex headers : Short name, Recommendation Index sort : recindex filter : type=tutorial

Recommendations¶

Note that these recommendations are my personal opinion. Please contact me

• if you have reviews or new sites
• if you're not okay with a recommendation
• if you're the author of a mentioned site (remove link, copyright, discussion, ...)
• etc...

The recommendation-indicator "REC" used below is a number between 1 and 10 visualized as a bar:

• \<progress=0> Not recommended to read, at best, don't click the link.
• ...
• \<progress=50> Use it with care!
• ...
• \<progress=100> The perfect godlike tutorial (I doubt I'll ever find it)

Detailed reviews¶

\<BOOKMARK:rv_linuxconfig>

linuxconfig.org Bash Scripting Tutorial¶

Article link: http://www.linuxconfig.org/Bash_scripting_Tutorial
Discussion link: http://www.linuxconfig.org/Talk:Bash_scripting_Tutorial UPDATE: Discussion page is gone.

Though the basic idea is nice, using flash terminal sessions and screenshots, there are many bugs or bad constructs.

Some stuff I didn't like there:

• uses external, unreliable command which instead of builtin type -p to determinate the location of a program
• lacks sane quoting
• uses function SOMENAME keyword instead of the common POSIX-compatible variant SOMENAME() to define a function
• uses backticks instead of $( ... ) for command substitution
• incorrectly uses an additional array to store positional parameters, disregarding that $@ already is array-like
• uses echo -e and the historical control character \c instead of modern printf
• uses for a in `seq 1 10` instead of a C-like counter loop for ((a=1; a <= 10; a++))
• the if/else stuff looks as if the test (or [ ...]) command is the only thing Bash can execute and check
• a for loop example that will explode on word-splitting
• arithmetic tests (the while/until loop examples) using the historical "old way" with test, not modern arithmetic components
• useless quoting of one-word strings (not that it hurts per se, but it shows that the author has no clue when to use quotes)
• a weird construct I don't understand (example for stdout/err redirection): grep -r hda6 * . 1>&2 stderr.txt

twkm commented some things on their http://www.linuxconfig.org/Talk:Bash_scripting_Tutorial, I linked this article there. UPDATE: Discussion page is gone.

Overall, if the author doesn't change the article, it's unusable from my point of view. At least unusable to teach sane Bash scripting.

UPDATE: Discussion is available directly below the article. I linked this page, but waiting for moderator approval. \<BOOKMARK:rv_qguide>

Quick Guide¶

Article link: http://www.panix.com/~elflord/unix/bash-tute.html
Discussion Link: not available

This article is usable as basic introduction into the Bash world. It doesn't teach you wrong things, and it uses correct syntax and explanations nearly everywhere. However, it's not usable as complete learning tutorial - but that is not the goal.

One point (I have to criticize something ;-) ):

• the article says that there are no C-styled for-loops in Bash, this is wrong (maybe the article is for a very old (pre 2.05b) Bash version)

\<BOOKMARK:rv_bprogintrohowto>

Bash Programming Introduction HowTo¶

Article link: http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html
Discussion link: not available; EMail: mikkey (AT) dynamo.com.ar

A few points:

• uses function SOMENAME instead of more common and most portable SOMENAME() to define functions
• wrong description of the if clause (says "the base [...] is if [expression];", which is wrong)
• a for-loop example will explode due to word splitting (for i in $( ls ) - evil!)
• the mentioned C-like for-loop is not the real C-like for-loop, it just calls seq(1)+
• Many syntax errors: The examples won't even parse correctly

I like the style this article is written in. If the points are fixed, it could be a really usable starting point for newbies. But at the moment it's unusable

\<BOOKMARK:rv_hypexrorg>

BASH Help at hypexr.org¶

Article link: http://www.hypexr.org/bash_tutorial.php
Discussion link: not available; EMail: scott (AT) hypexr.org

The article is usable to step into the shell world. It's not a tutorial per se, it will tell you some nice CLI-specific things like readline or completion.

Only one point:

• confusing description of the dotfiles

\<BOOKMARK:rv_abs>

Advanced Bash Scripting guide (ABS)¶

Article link: http://tldp.org/LDP/abs/html/
Discussion link: not available; EMail: thegrendel (AT) theriver.com

The only big problem I see with the ABS is, that the name doesn't match the reality. It doesn't teach advanced techniques. That doesn't mean the guide isn't good! It's one of the biggest, most complete and interesting Bash guides I've seen.

I don't want to write every point here that disturbs me. In general it's not that important since the mistakes or wrong assumptions it makes are minimal. Also I noticed that mistakes in example scripts vanish with time, the author polishes his work. Thanks Mr. Cooper.

The ABS is definitely worth reading to step deeper into the Bash commandline world of Linux (since many Linux-specific examples are there, they're unusable for Unices).

\<BOOKMARK:rv_bgb>

Bash Guide for Beginners¶

Article link: http://tldp.org/LDP/Bash-Beginners-Guide/html/
Discussion link: not available

Good introduction to bash and shell scripting, the guide is fairly complete and requires almost no previous knowledge other than be able to type some commands in a shell.

Some advice is a bit strange or outdated "Real Programmers - Most programmers will prefer to use the test built-in command" "Wherever possible, Bash users should try to use the syntax with angular brackets:(\$[ ])" but all in all a nice tutorial to get a good overview of shell programming starting from 0.

\<BOOKMARK:rv_linuxscriptv2>

Linux Shell Scripting Tutorial v2.0¶

Article link: http://bash.cyberciti.biz/guide/Main_Page
Discussion link: use the individual MediaWiki discussion pages

Additional problem: The author rates his shell skills as "9 of 10" in his CV. After reading this tutorial personally I'd rate him 3/10

This guide has some big problems. It seems to cover a lot of material but has some pretty nasty issues, too. Examples:

• ~~When showing how to echo variables, it shows echo $var and echo ${var} mostly without quoting.~~
• Lots of 'test' and not much '['. Not really a "problem" - more a style thing. But...
• test and [ and great, but what happened to \\? And test == is not used to check if two strings are equal. You use =.
• ~~How to deal with case insensitive matching mentions converting to lowercase with tr and doing a pattern like [tT][aA][rR]. I propose a third solution: shopt -o nomasematch~~
• The for loop examples reads like a how-not-to. for i in \<don't do this>: \< \$(ls /tmp/*)>, \<1 2 3 4 5>, \<\$files>, \<\$*>. Don't parse ls. Use {1..5}. Use an array for a list of files. Use quotes (and \$@).
• The infinite-while-loop example has him reimplementing the bash select builtin. Not bad for an exercise, but it ought to acknowledge that bash does it better.
• the description for compound commands is wrong: It shows 3 compound commands (grouping with and without subshell) where two of the examples are the same and the reason given for using ( ) applies equally to { }
• ~~the function definition focuses on the "function" keyword, which is the worst way~~
• The initial example page for pipes seems like a good list of examples of parsing things-you-do-NOT-want-to-parse
• ~~the page explaining special parameters misses \$@, which is very important~~
• ~~the page(s) about shell variables and environment doesn't even mention "environment" so far~~ some improvement.
• ~~backticks are not a quoting mechanism, they are a substitution mechanism. but that doesn't matter since he doesn't mention all quoting mechanisms anyways~~ some improvement, but the quoting page is still misleading
• ~~another hint that he doesn't know what he's talking about: It's said that command substitution is allowed inside backquotes (where backquotes are a quoting mechanism!) - backquotes are command substitution!~~
• etc. etc. etc. (nearly endless list, sadly)

Conclusion

Beside all the bashing (sorry!) above: I think the problem is the following, the author did a lot using the shell, and he knows many things. But he doesn't know and/or understand the underlying concepts of most of the material covered. This - in my personal opinion - disqualifies him as the author of a guide/tutorial for shell scripting.

But

The tutorial is under development. It improves here and there. But the code style and robustness problems still remain.

UPDATE: Over time, the author fixed a lot of things and created new chapters. From time to time, I'll visit again and re-check it.

\<BOOKMARK:rv_linuxcommand>

LinuxCommand.org: Writing shell scripts.¶

Article link: http://linuxcommand.org/writing_shell_scripts.php
Discussion link: not available

Bad:

• Difference between startup files .bash_profile and .bashrc is wrong ("Though placing your aliases and shell functions in your .bash_profile will work, it is not considered good form.")
• Reserved words (for the parser) are not disallowed as shell variable names (if the variable name is a reserved word, the reserved word takes precedence)
• It suggests the which command, which might be popular here and there, but should not be used for various reasons
• It says, variables with UPPERCASE names are constants, this might be a good style, but it's not a programming feature. Real "constants" are made from read-only variables
• Common mistake it shares with many other tutorials: The ANSI C escapes are not recognized by (normal) quoting mechanisms, it's the echo command that interprets them! On the other hand, it misses the quoting style that makes the shell interpret ANSI C escape sequences.
• It suggests the function keyword to define a function, which is correct, but bad style and unportable
• It could use getopts for positional parameters, at least as an "advanced example"
• It uses special parameters that represent positional parameters ($@) unquoted, and thus unsafe or buggy
• Slightly wrong: SIGKILL and the process stop signal can't be trapped. But that shouldn't really matter for daily shell coding
• "Creating safe temporary files", which is about creating a unique name, should mention tools like mktemp or the like
• It's far from complete, it "suddenly stops". Maybe it's still under development?

Good:

• Practise oriented
• It explains the behaviour of unquoted variable arguments to the test command in a nice, understandable way
• It does not use expr or let for arithmetic, good