lsof shell command in php denied

Question

i have the following code:

        $cmd="lsof | awk '{print $1 \" \" $2 \" \" $3 \" \" $9}'";
        $info = shell_exec($cmd);        
        $processors = preg_split('/\s?\n\s?\n/', trim($info));
        $processors = explode("\n",$processors[0]);
        foreach($processors as $processor){
           echo $processor."\n";
        }

when i run it on the command line i get positive results. however, when i run it on a php script i get:

systemd 1 root denied) for each $processor

IMHO not sure `awk` tag should be there for this post or not, may be `bash` tag since `lsof` is a shell command(internal or external)? — RavinderSingh13, Nov 06 '19 at 18:28

score 0 · Answer 1 · answered Nov 06 '19 at 18:26

If you look at the full output of lsof you'll see most lines look like:

COMMAND     PID   TID TASKCMD            USER   FD      TYPE             DEVICE  SIZE/OFF       NODE NAME
systemd       1                          root  cwd   unknown                                         /proc/1/cwd (readlink: Permission denied)

Because the user you're running as doesn't have permissions to look at processes that aren't its own.

Try: sudo lsof

score 0 · Accepted Answer · answered Nov 06 '19 at 18:26

When I given a try to your code posted, I too got the same errors(was able to re-produce the errors).

Then I tried to put only lsof in place of your complete lsof command with awk to see whats the complete error and I got following error.

COMMAND PID    USER   FD      TYPE DEVICE SIZE/OFF       NODE NAME
sh        1    root  cwd   unknown                            /proc/1/cwd (readlink: Permission denied)
sh        1    root  rtd   unknown                            /proc/1/root (readlink: Permission denied)
sh        1    root  txt   unknown                            /proc/1/exe (readlink: Permission denied)
sh        1    root NOFD                                      /proc/1/fd (opendir: Permission denied)
time      9    root  cwd   unknown                            /proc/9/cwd (readlink: Permission denied)
time      9    root  rtd   unknown                            /proc/9/root (readlink: Permission denied)

After that I googled and found a great link https://unix.stackexchange.com/a/109228 (cross site reference) which tells us that lsof is providing error since we don't have access on those files/commands and obviously we are NOT running command with root.

So to overcome this problem IMHO you could:

Run lsof command as sudo to get rid of errors, in case your user has sudo access to run this command.
In case you are NOT interested in root processes details then you could remove these errors by sending them to /dev/null.

lsof shell command in php denied

2 Answers2