On Sun, Jun 8, 2025 at 9:35 PM Zhaoxun Yan <yan.zhao...@gmail.com> wrote:
> it turned out to be an error misjudgement. The real line that caused
> trouble is this:
> s = er.Error()+string(out)
> The error is gone after I changed it to this line :
> s = fmt.Sprintf("%v %s", er, out)
>
The stdlib os.exec.Command()
<https://pkg.go.dev/os/exec@go1.24.4#Command>function
only returns a single value. Which should result in a compiler error since
your program expects two values. I'm going to guess that you are calling a
different function with that name which can return two values and the "er"
return value can be nil. Which would result in the "er.Error()" call to
dereference a nil value. So I think you have incorrectly diagnosed the
cause of the problem. The first statement does not correctly handle "er"
being nil. The "fmt.Sprintf()" correctly handles "er" being the nil value.
> On Fri, Jun 6, 2025 at 6:29 PM Zhaoxun Yan <yan.zhao...@gmail.com> wrote:
>
>> --------------------
>> panic: runtime error: invalid memory address or nil pointer dereference
>> [signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x6646f2]
>>
>> goroutine 1 [running]:
>> util.CommandArgs({0xc000093cb0?, 0x2?, 0xc000071380?})
>> /home/zxun/src/util/util.go:49 +0xf2
>> --------------------
>> This error occurred because package [main] uses a function called
>> "CommandArgs" from my self-built package [util] with args in another
>> package [conf] in the same directory. Package [util] got lost because it
>> does not know where is package [conf]
>> like this
>> [util] /home/zxun/src/util.go
>> [conf] /home/zxun/src/conf.go
>> [main] /home/zxun/src/main.go...
>> /home/zxun/src/go.mod:
>>
>> require(
>> util v0.0.0
>> ...
>> replace util => ../util
>>
>> The usage line in main.go:
>> fmt.Println( util.CommandArgs([]string{conf.IreportExec,
>> conf.IreportScript, "redis"}) )
>>
>> util.CommandArgs:
>>
>> func CommandArgs(args []string) string{
>> if len(args) ==0{
>> return "args are empty！"
>> }
>> var s string
>> if len(args) ==1{
>> out, er := exec.Command(args[0]).CombinedOutput()
>> s = er.Error()+string(out)
>> }else{
>> out, er := exec.Command(args[0],args[1:]...).CombinedOutput()
>> s = er.Error()+string(out)
>> fmt.Println(s)
>> }
>> return s
>> }
>>
>> So is my analysis correct? I have not seen s printed yet, because s shall
>> include "<nil>" at the beginning. I am using go1.18. If the cause is util
>> package cannot access a variable in conf, is it possible to walk around by
>> a deepcopy of the string array (which will be in package main)?
>>
>> Thanks in advance.
>>
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--
Kurtis Rader
Caretaker of the exceptional canines Junior and Hank
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