Meaning of code

Shell Programming and Scripting
1

Hi

Can anybody tell me what is the meaning of the following code?

i=4 j=1 k=0
[ $i -o $j -o $k ]Specialy meaning of this line
echo $?
[ $i -a $j -a $k ]Specialy meaning of this line
echo $?
[ $i -a $j -o $k ]Specialy meaning of this line
echo $?

Thanks in advance

Sas

2

First thing, please read the shell man pages.

i=4 j=1 k=0 Assign values 4, 1 and 0 to variables i, j, k
[ $i -o $j -o $k ] Test if one of the variable i j k is not emtty. Status $? is set to 1 if all variables are empty, and set to 0otherwise
echo $? Display exit status of the last command
[ $i -a $j -a $k ] Test that the variables i j k aren't empty. Status $? is set to 0 if all variables are empty, and set to 1 otherwise

3

That means if i write [ $x ], it checks whether the var x is null or not?Am i right???

4

You are right