How to get full cmd of a process in linux?

Question

My process cmd is very long because there are lots of arguments. Now I would like to check the full cmd. By using cat /proc/PROCESS_NUMBER/cmdline, the cmd is not fully shown. Is there any other way to see exactly full cmd in linux?

Answer 1

How long is your command line?

If it is in the megabyte range, you might perhaps recompile your kernel with a bigger ARG_MAX in your linux-3.*/include/linux/limits.h file. I put there

#define ARG_MAX  2097152    /* # bytes of args + environ for exec() */

^{(there might also be a way to set that limit dynamically, but I forgot how, and I could be wrong)}

I do like big ARG_MAX limit because I occasionally use the **/*.c global expansion feature of zsh which is my interactive shell.

Don't put a huge value in ARG_MAX; I would guess that you want to have it less than 2% of your available RAM.

Notice that /proc/*/cmdline contains null bytes. You might translate them, see this.

addenda

if for whatever reason you cannot afford a large command line, find some way and convention to avoid having such a large amount of program arguments. For instance, you could modify the invoked program to read some things from a file or some other source (database?). For example, some Unix programs (e.g. GCC) accept @filename to read options from some file named filename.