Shell script not picking up variable in if statement

Question

I have some code that looks like this:

 ################### - Let's call this section 1 if [ -n "$STUFF_JAVA" ]; then __LAUNCHER="$STUFF_JAVA" else __LAUNCHER="java" fi ################### - Let's call this section 2 if [ -n "$JAVA_HOME" ]; then # # echo "DEBUG: Using JAVA_HOME" _STUFF_JAVA_HOME="$JAVA_HOME" _STUFF_JAVA="$_STUFF_JAVA_HOME"/bin/$__LAUNCHER else echo "testing" fi ############## - Let's call this section 3 _STUFF_JAVA_HOME="$JAVA_HOME" _STUFF_JAVA="$_STUFF_JAVA_HOME"/bin/$__LAUNCHER ############## 

I don't understand why section 2 has issues setting the _STUFF_JAVA_HOME variable but section 3 does not? Do I need to use curly brackets or parenthesis somewhere?

I want my code to set the following variables:

_STUFF_JAVA_HOME _STUFF_JAVA 

I don't understand why it gets set in section 3 but not section 2.

For some reason, in section 2, it's not able to pick up the variable to determine the length...

Is there something I am missing?

(I am inexperienced with shell script. I am reading a book and have literally finished chapter 1.)

Answer 1

(base) jj@tb-jj:/$ ################### - Let's call this section 1 if [ -n "$STUFF_JAVA" ]; then __LAUNCHER="$STUFF_JAVA" else __LAUNCHER="java" fi ################### - Let's call this section 2 if [ -n "$JAVA_HOME" ]; then # # echo "DEBUG: Using JAVA_HOME" _STUFF_JAVA_HOME="$JAVA_HOME" _STUFF_JAVA="$_STUFF_JAVA_HOME"/bin/$__LAUNCHER else echo "testing" fi (base) jj@tb-jj:/$ echo "$_STUFF_JAVA" ./Some/Path/bin/java (base) jj@tb-jj:/$ echo "$_STUFF_JAVA_HOME" ./Some/Path 

It appears to be working fine. Can you be more specific with what the undesirable behavior actually IS? Also, you DO have a JAVA_HOME variable set, yes?

Also, I observe you've omitted the _ from _STUFF_JAVA in the Section 1 test and variable assignment. Is this intentional?

And, finally, a -n comparison is verifying that a variable is not null (or, more precisely, that it is a string whose length is -not zero).

This is distinct from a -z comparison (which is testing for a -zero-length string).

Consequently, note that [ -n "$my_var" ] will yield different results than [ -n $my_var ].

(base) jj@tb-jj:/$ [ -n "$BOB" ] && echo 1 # I will produce nothing, because you're expanding $BOB inside a blank \ # string, and then testing if a string is null (it's not). (base) jj@tb-jj:/$ [ -n $BOB ] && echo 1 # I will return 1, because you're now testing on an undeclared variable. 1 

(Note: I manually set my own JAVA_HOME to ./Some/Path before executing the first two sections of your code)