Setting resource limits from a shell script is commonly done with the ulimit command.
Shells provide it as a built-in, if they provide it at all. As far as I know, there is no non-built-in ulimit command. One could be implemented with the Linux-specific prlimit system call, but even that requires a fairly "recent" kernel version (circa 2010).
Depending on the kind of resource you want to limit, you may get away with what some shells such as dash provide: CPU, FSIZE, DATA, STACK, CORE, RSS, MEMLOCK, NPROC, NOFILE, AS, LOCKS. I.e. options tfdscmlpnvw, plus H for the hard limit, S for the soft limit, and a for all. Bash allows other resources to be limited.
Remember, if you rely on any non-standard behaviour or feature make sure you document it and, if feasible, check for it at run-time. ulimit is not required by POSIX:2001 to be implemented for the shell.