executing commands and going on

EchoAngel has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: executing commands and going on by davidrw (Prior) on May 13, 2005 at 16:05 UTC
I'm curious if `system("nohup echo HELLO WORLD &")` would work (btw, is that semi-colon really supposed to be before the ampersamp?) but what you're really looking for is fork() (`perldoc -f fork`). If you need to do more stuff in the original process when the long commands finally finish, that's a different issue...	[reply] [d/l] [select]
Re: executing commands and going on by polettix (Vicar) on May 13, 2005 at 16:16 UTC
If you want to print `HELLO WORLD;` [download] you have to escape the ";" character, which is interpreted as command separator by the shell: `system ("echo HELLO WORLD\\; &");` [download] Note the double backslash: you're using single quotes, so the backslash is the escaping character. The first escapes the second, which gets passed to the shell to escape the ";". There are almost infinite variations in your quoting approach, both within Perl and the shell, but it's left as an exercise :) Flavio (perl -e 'print(scalar(reverse("\nti.xittelop\@oivalf")))') Don't fool yourself.	[reply] [d/l] [select]
Re^2: executing commands and going on by ikegami (Patriarch) on May 13, 2005 at 16:45 UTC
`system(qq{echo "HELLO WORLD;" &});` [download] also does the trick.	[reply] [d/l]
Re: executing commands and going on by Belgarion (Chaplain) on May 13, 2005 at 16:05 UTC
Are you sure the command actually excutes at the shell? If I enter `echo HELLO WORLD; &` at the shell (bash in this case), I get the following error: bash: syntax error near unexpected token `&'	[reply]
Re: executing commands and going on by scmason (Monk) on May 13, 2005 at 16:15 UTC
Belgarion is right, this is not valid syntax. But what you really want to do is fork and execute the command in a sub-process. Like this: `$pid = fork; if ($pid) { #This is the parent, continue processing } else { #this is the child, so exec #which will replace the child exec("echo HELLO WORLD"); }` [download]	[reply] [d/l]
Re: executing commands and going on by bart (Canon) on May 13, 2005 at 18:29 UTC
It typically sounds like the problem that `echo` isn't actually a program, but an internal command from the shell. In that way, it's a FAQ. Try running something that actually has an associated program — or run a copy from the shell telling it to `echo` some text.	[reply]