How to parse /proc/pid/cmdline

Question

I'm trying to split the cmdline of a process on Linux but it seems I cannot rely on it to be separated by '\0' characters. Do you know why sometimes the '\0' character is used as separator and sometimes it is a regular space?

Do you know any other ways of retrieving the executable name and the path to it? I have been trying to get this information with 'ps' but it always returns the full command line and the executable name is truncated.

Thanks.

Answer 1

use strings

$ cat /proc/self/cmdline | strings -1 cat /proc/self/cmdline 

Answer 2

The /proc/PID/cmdline is always separated by NUL characters.

To understand spaces, execute this command:

cat -v /proc/self/cmdline "a b" "c d e" 

EDIT: If you really see spaces where there shouldn't be any, perhaps your executable (intentionally or inadvertently) writes to argv[], or is using setproctitle()?

When the process is started by the kernel, cmdline is NUL-separated, and the kernel code simply copies the range of memory where argv[] was at process startup into the output buffer when you read /proc/PID/cmdline.