Shell Programming and Scripting

Let me state something that i missed stating clearly.

I am not looking for a fix i.e the corrected commands and their locations. No !!

I m looking only to report the failing commands that fail due to the "command not found" or due to "illegal arguments".

I just need to report all failing commands in the script without executing the script on the server.

That's my requirement.

You can do that with proper error checking. It's a part of programming, the script can't do it for you.

Code:

die() {
        echo "$@" >&2
        exit 1
}

find ... || die "find did not work"

# etc

OK, now i am a bit baffled. In my experience the best error handling is the one where you dn't have to handle anything at all because you avoid the error altogether. Only the next best is to report the error properly.

This is quite easy: any responsible script programming includes checking the return codes of all the commands (at least the vital ones). This return code will be non-zero for:

a) - failing commands, regardless of why they fail, but there will be different error codes for the error condition
a1) - unknown argument/option
a2) - not enough rights
a3) - whatever else the error might be

b) - unknown commands

In case of b) the shell itself will return error 127, as you can easily test with a known and an unknown command:

Code:

# ls
[... some output...]
# echo $?
0
# /foo/bar/baz
/bin/ksh: /foo/bar/baz:  not found
# echo $?
127

You should be able to build an error handling function around that.

I hope this helps.

bakunin

So, all of you are asking me to write a separate script to report the failing commands.

Which means i will have to look for all command in 1000+ lines of unix shell script to figure out all the commands i use in there like:

Code:

ifconfig
ggrep
nawk
openssl
gzip

etc...

However, i wanted to know if it is somehow possible that my scripts are automatically check for all commands without executing the script & without me having to provide all commands in the check.

So, if any new script is introduced i should be able to validate all the command in that script without executing the script & without manually traversing line by line looking for unique commands in the scripts.

If it is not possible, then i will check for each command like some have suggested on this thread.

You might try one of the script compilers. Searching 'bash compiler' gets lots of hits.

No, but you might think a bit and find a more "computerised" way of achieving this goal. You can, for instance, write a small parser, which filters out all the shell keywords and other language constructs so that only commands are being left over, which you can then feed into a while-loop for instance to process as described below.

You can probably (but with less runtime-security) forego the parser and reduce it to a matter of sequential greps to arrive at the same list. Note, though, that this will be a more error-prone (altough more easily to achieve) alternative, because parsing adds context to the processed code which filtering doesn't (to add some theoretical background: the difference between Chomsky-Type 3 and Chomsky-Type 2 grammatics coming in here).


What exactly do you mean by "automatically"? If i remember correctly (Don Cragun may help out here) /usr/bin/dowhateverineed was not part of the POSIX standard last time i checked, so: no, you won't get that automatically. You will have to do work to achieve results like the rest of us.

Here is an idea: implement, what i proposed before, put that into a script, pass to this script the name of a another script you want to check, let the script go over the process of extracting commands and then, for every command found, execute a test if this command exists at the target system. This takes already care of the "command not found"-problem.

Here is another idea, which might sound a bit outlandish: STICK TO THE POSIX STANDARD! There are a lot of POSIX-certified platforms and even non-certified platforms will for most parts adhere to the standard. So, if you use only what is in this standard you will at most times be on the safe side even without complicated tests. If you want to use every obscure platform-specific speciality you are doomed to ultimately fail anyway, having tests or not. So, how about changing your working habits instead of wanting to change the world?

Frankly, i work in environments where i have to deal with up to a dozen different platforms (different OSes, different versions, etc.) and my scripts usually work even in these environments without problems (that is: problems coming from this diversity - my scripts are not flawless at all, but i don't have your problems). And 1000 lines of shell code is a typical size of one of my scripts, of which i have (and use) many dozens. My pity for you to have to manage 1000 lines of code is somewhat limited.

I hope this helps.

bakunin

No, to write your original one properly. If commands are failing left and right but it doesn't quit, you neglected to check a lot of return values.