vmtouch seems like a good tool for the job.
Highlights:
- query how much of a directory is cached
- query how much of a file is cached (also which pages, graphical representation)
- load file into cache
- remove file from cache
- lock files in cache
- run as daemon
vmtouch manual
EDIT:
Usage as asked in the question is listed in example 5 on vmtouch Hompage
Example 5
Daemonise and lock all files in a directory into physical memory:
vmtouch -dl /var/www/htdocs/critical/
EDIT2:
As noted in the comments, there is now a git repository available.
Short answer: you can't. Ports below 1024 can be opened only by root. As per comment - well, you can, using CAP_NET_BIND_SERVICE, but that approach, applied to java bin will make any java program to be run with this setting, which is undesirable, if not a security risk.
The long answer: you can redirect connections on port 80 to some other port you can open as normal user.
Run as root:
# iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
As loopback devices (like localhost) do not use the prerouting rules, if you need to use localhost, etc., add this rule as well (thanks @Francesco):
# iptables -t nat -I OUTPUT -p tcp -d 127.0.0.1 --dport 80 -j REDIRECT --to-ports 8080
NOTE: The above solution is not well suited for multi-user systems, as any user can open port 8080 (or any other high port you decide to use), thus intercepting the traffic. (Credits to CesarB).
EDIT: as per comment question - to delete the above rule:
# iptables -t nat --line-numbers -n -L
This will output something like:
Chain PREROUTING (policy ACCEPT)
num target prot opt source destination
1 REDIRECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8080 redir ports 8088
2 REDIRECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 redir ports 8080
The rule you are interested in is nr. 2, so to delete it:
# iptables -t nat -D PREROUTING 2
Best Answer
Use the split command.
split -b 22 m newfile.txt new
would split the file "newfile.txt" into three separate files called newaa, newab and newac each file the size of 22 MB.