Negate if condition in bash script

Question

I m new to bash and I m stuck at trying to negate the following command   wget -q --tries 10 --timeout 20 --spider http   google com if       -eq 0     then         echo  Sorry you are Offline          exit 1   This if condition returns true if I m connected to the internet  I want it to happen the other way around but putting   anywhere doesn t seem to work

User · Answer

Better  if   wget -q --spider --tries 10 --timeout 20 google com then   echo  Sorry you are Offline    exit 1 fi

User · Answer

If you re feeling lazy  here s a terse method of handling conditions using     or  and  amp  amp   and  after the operation   wget -q --tries 10 --timeout 20 --spider http   google com        echo  Sorry you are Offline   amp  amp  exit 1

User · Answer

You can use unequal comparison -ne instead of -eq   wget -q --tries 10 --timeout 20 --spider http   google com if       -ne 0     then     echo  Sorry you are Offline      exit 1 fi

User · Answer

Since you re comparing numbers  you can use an arithmetic expression  which allows for simpler handling of parameters and comparison   wget -q --tries 10 --timeout 20 --spider http   google com if          0     then     echo  Sorry you are Offline      exit 1 fi   Notice how instead of -ne  you can just use     In an arithmetic context  we don t even have to prepend   to parameters  i e    var a 1 var b 2    var a  lt  var b     amp  amp  echo  a is smaller    works perfectly fine  This doesn t appply to the    special parameter  though   Further  since           evaluates non-zero values to true  i e   has a return status of 0 for non-zero values and a return status of 1 otherwise  we could shorten to  if           then   but this might confuse more people than the keystrokes saved are worth   The           construct is available in Bash  but not required by the POSIX shell specification  mentioned as possible extension  though    This all being said  it s better to avoid    altogether in my opinion  as in Cole s answer and Steven s answer

User · Answer

You can choose   if       -ne 0     then         -ne  not equal  if         -eq 0     then       -eq  equal  if         -eq 0     then     inverts the return of the following expression  respectively

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