Just had a first look at shellcheck.
It looks like it makes suggestions in addition to the real faults that are found by sh -nx
Well here is the code that shellcheck checked:-
And I decided to [ba]sh -n BUG1.sh and it says it is syntactically correct.
Again /Me shrugs...
Have I discovered a general SHELL bug, although esoteric is STILL a bug?
Are these arithmetic related ERRORs capable of being hacked from the outside?
(I have no idea as I am a mere amateur.)
Why in fact does bash -n NOT pick it up on at least my OSX 10.11.6 version of 'bash'?
Location: Saint Paul, MN USA / BSD, CentOS, Debian, OS X, Solaris
Posts: 2,288
Thanks Given: 430
Thanked 480 Times in 395 Posts
Static checking
Hi.
The definition for the syntax check is:
Here is how I see this.
If no code is executed, then variables are not defined. If there is no execution, then commands like [ are not executed, and there can be no check for the internal syntax of expressions after [ -- which is the same as command test.
I think the syntax check of the -n option can only check structural syntax. Below are some examples that I thought of, and there are probably more.
So to debug a code, I think a preliminary run with bash -n can be used to help eliminate gross errors in structure, missing elements like then or do, unmatched parens and quotes, etc. Then the script can be run to get rid of the internal syntax errors, like those mentioned above with test and friends, and finally shellcheck to look at other items.
So check, run, check would be how I would approach this if I were to write long sections of code (my longest shell script is just under 800 lines, but most are far smaller). There might be instances where check, check, run might be more useful. It depends on the code and coder.
Best wishes ... cheers, drl
Here are some samples that bash -n can catch as noted by script run-all:
producing:
Hi drl...
How about this then:- $[ ( expression ) ] is runtime identical to $(( expression )) , yes...
If the error reports are different then does that imply that they might not be runtime identical?
If not then explain why some of these errors are different?
These old arithmetic expressions were what brought about this thread in the first place.
At this pont I am going to bow out gracefully and keep a watchful eye on this thread.
Location: Saint Paul, MN USA / BSD, CentOS, Debian, OS X, Solaris
Posts: 2,288
Thanks Given: 430
Thanked 480 Times in 395 Posts
Hi, Barry.
On a system like:
there is no mention of $[ in the man page. There might be in your version 57.
Interactive results there:
The man page for a modern bash 4.3.30 notes:
The man page for modern dash 0.5.7-4+b1 does not mention $[ at all.
For this code:
Both dash -n and bash -n return nothing on that file.
Executing the code first with bash on that file produces:
then dash:
So my conclusion is that $[ is not portable, it is not equivalent to $((, and it will be removed from future versions of bash, as has been done with dash currently.
Judging from the output comparing $(( to $[, I would say that they have either: a) differing syntax requirements, or b) old code for $[ was not updated. I tend to think the former.
So I would say, in addition to my suggested sequence in a previous post for bashcheck / bashrun / shellcheck, I would advise changing $[ to $((
If you are writing to the lowest common denominator, say sh (which may link to dash as it does in Debian), then you might want look at script checkbashisms to identify bash-only constructs.
Quote:
Originally Posted by wisecracker
At this pont I am going to bow out gracefully and keep a watchful eye on this thread.
Yeah, me too
Best wishes ... cheers, drl
Last edited by drl; 10-04-2016 at 10:38 AM..
Reason: Correct minor typos.
Hello All,
Not sure why this is happening...
When the following If Statement is evaluated for some reason it is creating a file in the CWD called '0'. I've seen this happen
before, just not in an If Statement...
CODE:
if
then
DIR_NAME="$1"
DIR_SIZE=0
STATUS=""
else... (3 Replies)
Hello All,
I'm trying to extract the lines between two consecutive elements of an array from a file.
My array looks like:
problem_arr=(PRS111 PRS213 PRS234)
j=0
while } ]
do
k=`expr $j + 1`
sed -n "/${problem_arr}/,/${problem_arr}/p" problemid.txt
---some operation goes... (11 Replies)
Hi all,
How am I read a file, find the match regular expression and overwrite to the same files.
open DESTINATION_FILE, "<tmptravl.dat" or die "tmptravl.dat";
open NEW_DESTINATION_FILE, ">new_tmptravl.dat" or die "new_tmptravl.dat";
while (<DESTINATION_FILE>)
{
# print... (1 Reply)
CA_RELEASE has a value of 6. I need to check if that this is a numeric value. if not error.
source $CA_VERSION_DATA
if * ]
then
echo "CA_RELESE $CA_RELEASE is invalid"
exit -1
fi
+ source /etc/ncgl/ca_version_data
++ CA_PRODUCT_ID=samxts
++ CA_RELEASE=6
++ CA_WEEK_NO=7
++... (3 Replies)
#!/bin/bash
if then
#echo "infinite loop"
exit 0
fi
when I run this file I get the following error:
./test_infinite_loop: line 5: syntax error near unexpected token `fi'
./test_infinite_loop: line 5: `fi'
:confused: (4 Replies)
Is it possible to combine a regular expression with a aritmetical expression? For example, taking a 8-numbers caracter sequece and casting each output of a grep, comparing to a constant.
THX! (2 Replies)