Shell command execution and return value

ROOT
1

Dear all,

I don’t understand something with the TSystem commands to execute a shell command.

Here is a shell session with a successful and a failed command :

[code]>ls

echo ? 0 ls ---- <error> echo ?
2[/code]

In ROOT, I get different return code :

root [7] int i = gSystem->Exec("ls") <output> root [8] i (int)0 root [9] int i = gSystem->Exec("ls --------") <error> root [10] i (int)512
You see that I get 512 instead of 2. Why is that ?

Related question : I can get the output of a command by using GetFromPipe(). How to get both the output and the return value ?

Thank you
Barth

2

In case of Unix … the TUnixSystem::Exec simply calls the standard “system” library function. For details of the “return value” see:
man 3 system
man 2 wait
(Try also to print “WEXITSTATUS(512)”.)

Looking at the source code of the TSystem::GetFromPipe … I’m afraid that the “return value” from the final TUnixSystem::ClosePipe call is lost. You would need to write your own routine which “mimics” the original one, but which also saves this value somewhere (for later usage in your code).

3

Hello,

Thank you for your reply. I have created a Savannah ticket to ask for an improved GetFromPipe method.

For the time being, and in order not to duplicate and modify a ROOT method, I will simply use Exec and save the output in a file.

Best regards,
Barth