mjhjmtu

I want to check if a file exists in HDFS or not and capture it in the variable SUCCESS_FILE_CHECK, i.e., if file exists the SUCCESS_FILE_CHECK should be 0 else it can be any other value.

$ SUCCESS_FILE_CHECK=$(hdfs dfs -test -e hdfs://path/to/file)
$ echo $SUCCESS_FILE_CHECK

$ hdfs dfs -test -e hdfs://path/to/file # given this file exists
$ echo $?
0

My understanding was, if the file exists then the command within the subshell $() will return 0 and SUCCESS_FILE_CHECK will be initialized to 0. But instead when I do echo $SUCCESS_FILE_CHECK, I get nothing (irrespective of whether the file exists or not).

Also take a look at the following script:

$ SUCCESS_FILE_CHECK=$(hdfs dfs -test -e hdfs://path/to/file) # given this file exist
$ echo $?
0
$ SUCCESS_FILE_CHECK=$(hdfs dfs -test -e hdfs://path/to/file2) # given this file DOES NOT exist
$ echo $?
1

In this case, I expected the output of both the echo to be 0 since $? prints the status of the last command executed and the last command executed is an assignment (a=b) which should always return true, since the command did run successfully.

Can someone help me understand this behaviour?