ruby system command check exit code
RubyCommandExitExit CodeRuby Problem Overview
I have a bunch of system calls in ruby such as the following and I want to check their exit codes simultaneously so that my script exits out if that command fails.
system("VBoxManage createvm --name test1")
system("ruby test.rb")
I want something like
system("VBoxManage createvm --name test1", 0)
<-- where the second parameter checks the exit code and confirms that that system call was successful, and if not, it'll raise an error or do something of that sort.
Is that possible at all?
I've tried something along the lines of this and that didn't work either.
system("ruby test.rb")
system("echo $?")
or
`ruby test.rb`
exit_code = `echo $?`
if exit_code != 0
raise 'Exit code is not zero'
end
Ruby Solutions
Solution 1 - Ruby
From the documentation:
> system returns true
if the command gives zero exit status, false
for
> non zero exit status. Returns nil
if command execution fails.
system("unknown command") #=> nil
system("echo foo") #=> true
system("echo foo | grep bar") #=> false
Furthermore
> An error status is available in $?
.
system("VBoxManage createvm --invalid-option")
$? #=> #<Process::Status: pid 9926 exit 2>
$?.exitstatus #=> 2
Solution 2 - Ruby
For me, I preferred use `` to call the shell commands and check $? to get process status. The $? is a process status object, you can get the command's process information from this object, including: status code, execution status, pid, etc.
Some useful methods of the $? object:
$?.exitstatus => return error code
$?.success? => return true if error code is 0, otherwise false
$?.pid => created process pid
Solution 3 - Ruby
system
returns false
if the command has an non-zero exit code, or nil
if there is no command.
Therefore
system( "foo" ) or exit
or
system( "foo" ) or raise "Something went wrong with foo"
should work, and are reasonably concise.
Solution 4 - Ruby
You're not capturing the result of your system
call, which is where the result code is returned:
exit_code = system("ruby test.rb")
Remember each system
call or equivalent, which includes the backtick-method, spawns a new shell, so it's not possible to capture the result of a previous shell's environment. In this case exit_code
is true
if everything worked out, nil
otherwise.
The popen3
command provides more low-level detail.
Solution 5 - Ruby
One way to do this is to chain them using and
or &&
:
system("VBoxManage createvm --name test1") and system("ruby test.rb")
The second call won't be run if the first fails.
You can wrap those in an if ()
to give you some flow-control:
if (
system("VBoxManage createvm --name test1") &&
system("ruby test.rb")
)
# do something
else
# do something with $?
end
Solution 6 - Ruby
Ruby 2.6 added option to raise exception in Kernel#system:
system("command", exception: true)
Solution 7 - Ruby
> I want something like
>
> system("VBoxManage createvm --name test1", 0)
<-- where the second parameter checks the exit code and confirms that that system call was successful, and if not, it'll raise an error or do something of that sort.
You can add exception: true
to your system
call to have an error raised on non 0 exit codes.
For example, consider this small wrapper around system
which prints the command (similar to bash -x
, fails if there's a non 0 exit code (like bash -e
) and returns the actual exit code:
def sys(cmd, *args, **kwargs)
puts("\e[1m\e[33m#{cmd} #{args}\e[0m\e[22m")
system(cmd, *args, exception: true, **kwargs)
return $?.exitstatus
end
To be called like: sys("hg", "update")
If you want to call a program that uses a different convention for exit codes, you can suppress raising the exception:
sys("robocopy", src, dst, "/COPYALL", "/E", "/R:0", "/DCOPY:T", exception: false)
You can also suppress stdout and stderr for noisy programs:
sys("hg", "update", "default", :out => File::NULL, :err => File::NULL)