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script op is different


 
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# 1  
Old 08-29-2009
script op is different

Consider the following script..

Code:
str1="Good"
str2="Bad"
str3=
[ $str1 = $str2 ]
echo $?
[ $str1 != $str2 ]
echo $?
[ -n $str1 ]
echo $?
[ -z "$str3" ]
echo $?
[ -z $str3 ]
echo $?
[ "$str3" ]
echo $?

When I executed this, the o/p is

Quote:
asit@asit-desktop:~/script$ sh str1.sh
1
0
0
0
0
1
But in my book, the op is totally different,

Quote:
1
0
0
0
test: argument expected
What should I do ?? Which one I should accept ??
# 2  
Old 08-29-2009
-deleted-
# 3  
Old 08-29-2009
If you understand what is being tested, you'd know which one to accept. Plus, you would accept the one you actually see executed, right?

Code:
[ $str1 = $str2 ]

tests to see if $str1 is equal to $str2. They are not so return false (1).

Code:
[ $str1 != $str2 ]

tests to see if $str1 is not equal to $str2. They are not so return true (0).

Code:
[ -n $str1 ]

tests to see if $str1 is not empty/null. It is not so return true (0).

Code:
[ -z "$str3" ]
[ -z $str3 ]

These are identical and test to see if $str3 is null. It is so return true (0).

Code:
[ "$str3" ]

tests to see if $str3 in not empty (-n is implied). It is so return false (1).

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