命令替换，bash和管道出错

Question

Using CentOS 6.4

Executing:

var1=$(softnas-cmd checkupdate | jq .success)

give me an error:

"parse error: Invalid numeric literal at line 1, column 9"

if I execute var1=$(softnas-cmd checkupdate) followed by echo $var1 I get:

{"success" : true, "session_id" : 1935, "result" : {"success":true,"msg":"You are running the latest version","records":{"version":"2.1.3.el6.x86_64","newversion":"2.1.3.el6.x86_64","updateavailable":false,"msg":"You are running the latest version"},"total":4}}

if I then execute var2=$(echo $var1 | jq .success) this works and I get the expected: true

ultimately I want to do this:

if [ $(softnas-cmd checkupdate | jq .succcess) = "true" ]; then
   echo "update required"
   ...
fi;

can anyone tell me how to format the command substitution so I can execute in one shot?

Thanks

Answer 1

Are you trying to parse the true/false after the string "updatevailable"? If so, try this:

res=`softnas-cmd checkupdate | sed -n "s/.*updateavailable\":\([tf][a-z]*\),.*/\1/p"`; 
if [ "$res" == "true" ]; then 
    echo "update required" ... 
fi;

if you are, however, trying to parse the true/false after the first "success" string, then:

res=`softnas-cmd checkupdate | sed -n "s/.*\"success\" : \([tf][a-z]*\), .*/\1/p"`; 
if [ "$res" == "true" ]; then 
    echo "update required" ... 
fi;

and parsing the second "success" string would be:

res=`softnas-cmd checkupdate | sed -n "s/.*\"success\":\([tf][a-z]*\), .*/\1/p"`; 
if [ "$res" == "true" ]; then 
    echo "update required" ... 
fi;