Search code examples
shellif-statementshexitstatus

Bourne: if statement testing exit status

What is the difference:

if IsServerStarted ; then ...

and

if [ IsServerStarted -eq 0 ] ; then ...

Seems to me that these two statements should be equivalent? Strangely the second statement is always true.

Solution

  • The following runs the shell function or executable in $PATH named IsServerStarted, and if its exit code is 0 (i.e. true), runs the then branch. If such a function or executable does not exist, the exit code will be non-0 (i.e. false) and the then branch will be skipped.

    if IsServerStarted ; then ...

    The following has [ (aka test) check whether IsServerStarted is an integer equal to 0, which (IsServerStarted not even containing a single digit) is always false. Thus, [ exits with a non-0 (i.e. false) code and the then branch is always skipped.

    if [ IsServerStarted -eq 0 ] ; then ...