Answer by Jay for Does linux have any measures to protect against fork bombs?

Yes, although it may not be enabled by default on your system. The setrlimit system call defines system limits -- including the number of processes per user.

Let's look at it first in the kernel API (since you mentioned "linux"): you can use the manpage for setrlimit, which will tell you to do something like

#include <sys/resource.h>...struct rlimit  r;rnew.r_cur = 40;rnew.r_max = 50;setrlimit(RLIMIT_NPROC,&r);

This will set the maximum processes per user (RLIMIT_NPROC) to 40 (soft limit) and 50 (hard limit).

Now, from the shell, if you use bash, you can use the ulimit built-in command:

ulimit -u29089

You can set the limit by passing it as an argument:

ulimit -u 100

ulimit --help will show you that there are several other limits you can set (one which may be of interest is the maximum number of file descriptors used by the user).