I am trying submit to $process the result of this system call
my $process= system "adb shell ps | egrep adb | awk '{print $1}' ";
but when print " $process \n"; I have got zero
Any suggestions
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3 Answers
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I don't think perl captures output when you use system() calls.
Try wrapping it in backticks instead:
my $process = `adb shell ps | egrep adb | awk '{print $1}'`;
Rob Williams
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If you run that command at a shell prompt, what does it give you? – Rob Williams Mar 24 '11 at 07:36
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When I run it on my ubuntu machine I have got root – Koby Mar 24 '11 at 07:39
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Try $2, then, instead of $1. It sounds like it's giving you the process owner instead of the process id. – Rob Williams Mar 24 '11 at 07:48
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The solution is to call without system like this `adb shell ps | egrep adb | awk '{print \$2}' ` – Koby Mar 24 '11 at 07:50
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The return value of system() is the exit status of the program (here). Use backtick operation instead:
$process = `...`;
pmod
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Ok It's look like that $process getting the egrep adb result without consider the awk – Koby Mar 24 '11 at 07:45
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So when calling my $process= `adb shell ps | egrep adb | awk '{print \$1}` I have got what I need, Thanks – Koby Mar 24 '11 at 07:48
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I just found a much more detailed explanation on SO itself. Editing to add that link - What's the difference between Perl's backticks, system, and exec?
What pmod has mentioned is correct. Since I have been doing a bit of reading on this lately, just adding a comment with what I found:
system
executes a command and your perl script is continued after the command has finished. It returns the exit status of the command.
backticks - ` `
This is kind of like system, executes the command which you launch and waits for it to return. However, unlike system, returns STDOUT for the command. Which I presume is what you are looking for here.
exec
replaces current with new process and doesn't return anything.
Hope that helps ...
