CentOS - Feb 2015 - C5 BASH IF

Being new to some aspects of BASH, I tried to reduce the quantity of
scripts by introducing a comparison test into an existing working
script.

The script refused to work until I placed [ ] around the actual test.
The second test, in the same script, misfunctioned until I removed the
[ ] around the second test.

----------------------------
NON WORKING first comparison

5 if $dir="law"   
6   then
7        www="law"
8        dir=${file:0:5}
9 else
10        www="www/s"
11 fi

Error message = /root/bin/.us: line 5: law=law: command not found

---------------------------------

WORKING first comparison

5 if [ $dir="law" ]
6   then
7        www="law"
8        dir=${file:0:5}
9 else
10        www="www/s"
11 fi

------------------------------------

NON-WORKING second comparison

15 if [ $file='law00.css' ]
16   then
17        file=$dir/$file
18        echo "css"
19 else   
20        file=$dir/$file\.php
21        echo "no css"
22 fi
23 #----------------------------

Every comparison in the second test, including wrong comparisons,
satisfy the test and caused the 'css' display.

When line 15 was changed to

	15 if [ $file='law00css' ]

everything continued to match including items with no 'css' in the file
name.


Baffled.

Are C5 BASH scripts restricted to only 1 IF comparison ?




-- 
Regards,

Paul.
England, EU.      Je suis Charlie.

On Fri, Feb 13, 2015 at 11:26 PM, Always Learning <centos at u64.u22.net>
wrote:
> Being new to some aspects of BASH, I tried to reduce the quantity of
> scripts by introducing a comparison test into an existing working
> script.
>
> The script refused to work until I placed [ ] around the actual test.
> The second test, in the same script, misfunctioned until I removed the
> [ ] around the second test.
>
I think you are missing some very basic concepts here.  First, the
shell likes to parse things separated by white space.  Second, [ is a
synonym for test which is a build-in version of /bin/test, so try 'man
test' for the syntax of tests.   And third, you generally should use
double quotes around variables in tests so they continue to exist as
an empty string if the variable happens to not be set.

-- 
   Les Mikesell
      lesmikesell at gmail.com

On Sat, 2015-02-14 at 05:26 +0000, Always Learning wrote:
> NON-WORKING second comparison
> 
> 15 if [ $file='law00.css' ]
> 16   then
> 17        file=$dir/$file
> 18        echo "css"
> 19 else   
> 20        file=$dir/$file\.php
> 21        echo "no css"
> 22 fi
> 23 #----------------------------
> 
> Every comparison in the second test, including wrong comparisons,
> satisfy the test and caused the 'css' display.
> 
> When line 15 was changed to
> 
> 	15 if [ $file='law00css' ]
> 
> everything continued to match including items with no 'css' in the
file
> name.
I re-ran the script with 'set -x' for

16 if  [ $file='law00css' ]
17   then
18        echo $file
19        echo "css"
20 else
21        echo "no css"
22 fi     

and received:-

+ '[' law45p07a01=law00css ']'
+ echo law45p07a01
law45p07a01
+ echo css
css



-- 
Regards,

Paul.
England, EU.      Je suis Charlie.

On Fri, 2015-02-13 at 23:46 -0600, Les Mikesell wrote:
> I think you are missing some very basic concepts here.  First, the
> shell likes to parse things separated by white space.  Second, [ is a
> synonym for test which is a build-in version of /bin/test, so try 'man
> test' for the syntax of tests.   And third, you generally should use
> double quotes around variables in tests so they continue to exist as
> an empty string if the variable happens to not be set.
Thanks for that.  I assumed if test 1 worked, so would test 2.

Have re-run test 2 with

> 16 if  [ $file = "law00css" ]
> 17   then
> 18        echo $file
> 19        echo "css"
> 20 else
> 21        echo "no css"
> 22 fi
and got
> + '[' law45p07a01 = law00css ']'
> + echo 'no css'
> no css
> + exit
which is correct (for the first time). It seems that following your
good advice and plonking spaces around the = has solved the problem.

Thank you very much. Now I can go to bed a satisfied person :-)

-- 
Regards,

Paul.
England, EU.      Je suis Charlie.

On 02/13/2015 11:47 PM, Always Learning wrote:
> I re-ran the script with 'set -x' for
>
> 16 if  [ $file='law00css' ]
> 17   then
> 18        echo $file
> 19        echo "css"
> 20 else
> 21        echo "no css"
> 22 fi
>
> and received:-
>
> + '[' law45p07a01=law00css ']'
> + echo law45p07a01
> law45p07a01
> + echo css
> css
Correct. You invoked the test command with a single argument, the
string "law45p07a01=law00css". With a single argument, the test is
just whether that argument in non-null, which it is. To perform
a comparison you need 3 separate arguments (2 operands and an
operator), not 1.

-- 
Bob Nichols     "NOSPAM" is really part of my email address.
                 Do NOT delete it.