I'm doing some examples following this tutorial and I was curious to know if there is this kind of function in shell (var_dump PHP) because I Googled and found nothing.

For following these tutorials I'm trying to do something useful and have the following example:

pids=$(ps -C pidgin -o pid=)
if [ -z $pids ];
         echo "have pids" $pids
         echo "do not have pids" $pids

But I cannot validate the variable 'pids' even with "-n or -z or ! $pids" always prints the number of pidgin pids even in if or else condition Running on terminal show this:

bash: [: 2480: binary operator expected
do not have pids 2480 20700

How can I property make this sentence work for this example?

  • 2
    I'm not sure where to begin, there is so much wrong here. First, your title seems to be about things that aren't even in the question. Second, you point to a tutorial about things that aren't even in the script you posted. You don't say which OS and shell you are using, so I guessed. Then the script seems to have a space that doesn't belong there (in the if). You also need quoting there to make a valid expression. Could you please edit the text to fix at least some of these, and also what you are expecting (rather than what [ was expecting), and maybe someone can help. – MAP Jul 15 '16 at 2:00
  • 2
    To at least make the script run properly, change the first line to pids="$(ps -C pidgin -o pid=)" and change the second line to if [ -z "$pids" ];. – Lawrence Velázquez Jul 15 '16 at 2:07
  • You may want to take a look at the Debugging Bash scripts section of the Bash Guide for Beginners. – user1737246 Jul 15 '16 at 3:05
  • this work too, and sorry about my English, google translate help me. – rafaelphp Jul 15 '16 at 3:23
  • @Lawrence Velázquez your first change (v="$(...)" instead of v=$(...)) makes no difference; it's purely cargo-cult. – pizdelect Jun 28 at 5:45

You should quote it like this:

if [ -z "$pids" ]

If you ever find yourself using a variable outside of quote marks, you're probably doing it wrong.

  • Thanks, this work, now I got the real result work, I understand how it works like, was my mistake. thanks. – rafaelphp Jul 15 '16 at 3:22

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