LinuxQuestions.org - [SOLVED] Opposite to expected response in awk

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Opposite to expected response in awk

I am using following awk code on a file called dirlist. However, it is giving reverse response- printing out directories if they are there when asked about not there and vice versa:

Code:

$ cat dirlist

/root

/boot

/sys

/a_dir

/b_dir



# TRYING TO PRINT IF DIRECTORY IS PRESENT: 

$ cat dirlist | awk ' { if ( system(" [ -d " $1 " ] ")  ) print $1 } '

/a_dir

/b_dir



# TRYING TO PRINT IF DIRECTORY IS ABSENT: 

$ cat dirlist | awk ' { if ( system(" [ ! -d " $1 " ] ")  ) print $1 } '

/root

/boot

/sys

Where is the problem. Thanks for your insight.

system() returns the command's exit status. "[ -d a_dir ]" has an exit status of 0 when a_dir exists, and 1 when it doesn't exist.

Now when the if condition is nonzero, awk considers it as true. So, a nonexisting directory returns 1, which is true.

Perfect explanation.