Go to command mode Esc, then run :!unix_command. Anything run from the : prompt starting with a bang ! will be run as a unix shell command. You'll be shown the output and allowed to hit a key to get back to your work in vim.
If you have text selected in visual mode and want to send it TO a command as STDIN, hit !! and enter your command. The results of the command will replace the text you have selected.
Daniel Andersson's comment about POSIX is the real answer here: there is a standard called POSIX which defines the core of a UNIX-like system, both in terms of shell commands and system calls. In theory, if you write software to the POSIX spec, it should be possible to compile and run it on any UNIX, Linux, BSD etc system.
http://pubs.opengroup.org/onlinepubs/009695399/mindex.html will give you a definitive answer as to what constitutes POSIX, but that's not a useful answer for practical purposes. Someone else may have good command references for common differences between Linux systems and other UNIX-like systems.
One specific example: "killall" on Linux kills all processes with a particular name. On Solaris, it shuts the system down. Important not to use the wrong one.
Best Answer
Go to command mode Esc, then run
:!unix_command. Anything run from the:prompt starting with a bang!will be run as a unix shell command. You'll be shown the output and allowed to hit a key to get back to your work in vim.If you have text selected in visual mode and want to send it TO a command as STDIN, hit
!!and enter your command. The results of the command will replace the text you have selected.