How to measure the execution time of a function, say f: ‘a -> ‘b in OCaml? This small OCaml function is handy: let time f = let t = Unix.gettimeofday () in let res = f () in Printf.printf “Execution time: %f secondsn” (Unix.gettimeofday () -. t); res ;; The gettimeofday returns a float representing…
Do you know how to display chinese character in lxterminal? I tried to install lxterminal on my workstation and it seems display Chinese characters well: FYI, my Linux system is Fedora 21. The lxterminal version: $ rpm -q lxterminal lxterminal-0.1.11-10.fc21.x86_64 Not sure what’s the reason why it does not work for you. You may check…
How to list all running system service on Linux Mint 17.1? You can use initctl to list all services: initctl list
How to log connections hitting certain rules in iptables on Linux? Like the one that are dropped because of too frequently creating SSH connections. You can create a new chain named LOGNDROP that log the connections and drop them, then pass the connection to be redirected to the LOGNDROP chain. $tables -N LOGNDROP # Connections…
ELPA manages packages for Emacs nicely. But, how to upgrade packages installed by ELPA in Emacs? Within Emacs, list all packages by M-x list-packages and it will automatically refresh the archive contents. Then, press U to mark all upgradable packages to be upgraded. Last, press x to perform the new updates. Emacs will then download…
How to use iptables to limit rates new SSH incoming connections from each IP on Linux? For example, at most 6 SSH connection attempts every 60 seconds. You may use these rules (skip the first one, if you have set the basic rules): for tables in iptables ip6tables ; do # Allow established inbound connections…
How to configure iptables and make the configuration persistent across system restarting on Linux Mint 17.1? You can use the ‘iptables-persistent’ tool. To install iptables-persistency pachage: sudo aptitude install iptables-persistent The you can manipulate the iptables by the ‘iptables’ command. To save the current iptables rules: sudo /etc/init.d/iptables-persistent store It will store the rules for…
How to install musl libc on Linux Mint 17/Ubuntu 14.04? You can install musl libc on Linux Mint 17 by sudo aptitude install musl musl-dev musl-tools One note: If you want to install a newer version of musl libc than the one from Ubuntu repo, you can use this ppa: https://launchpad.net/~bortis/ archive/ubuntu/musl by sudo add-apt-repository…
How to find the available packages’ versions with aptitude on Linux? With aptitude, you can use this command to show the available versions of a package: aptitude versions <package name> In the console GUI, aptitude also show the versions. You may also simulate installation of a package and see which version will be installed: aptitude…
Alt key seems not work in xterm. Alt is important for Emacs. How to make Alt key work in xterm? Put this in your ~/.Xresources file: XTerm*eightBitInput: false XTerm*eightBitOutput: true Remember to make it take effect after you change the ~/.Xresource without restarting the X server by xrdb -merge ~/.Xresources
How to exclude directories with certain names like “cache” from rsync on Linux during backup? The “cache” directory may in many different paths, such as file1/cache/ or file2/cache/, and adding all “cache” directories to rsync command is not a doable way. You can use rsync with –exclude=cache/ like rsync -avxP –exclude=cache/ /path/to/src/directory/ /path/to/dst/dir/
Currently, I have created my branch dev-harry but I cannot pull it successfully as follows. harryxiyou@common_vm ~/forest/kvplus/kvplus $ git branch * dev-harry master rc harryxiyou@common_vm ~/forest/kvplus/kvplus $ git pull You asked me to pull without telling me which branch you want to merge with, and ‘branch.dev-harry.merge’ in your configuration file does not tell me, either….
How to find the number of files in each sub-directories of a directory on Linux? For example, . ├── a19 ├── a8 ├── d2 ├── ecfddd └── t1 The number of sub-directories can be quite large. How to find the number of files in each sub-directories here? You can use this piece of script to…
My Linux distro is Linux Mint 17 (Ubuntu 14.04.1 LTS (Trusty Tahr)). I am using NetworkManager. The old trick does not work: $ cat /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND — YOUR CHANGES WILL BE OVERWRITTEN nameserver 127.0.1.1 If you are using…
How to play 3D movies in MPlayer on normal screen (2D)? You can play 3D movies on 2D screen by mplayer -vo gl_stereo=3 your.movie.file For the gl:stereo=3 option, check MPlayer man page: stereo=value Select a method for stereo display. You may have to use -aspect to fix the aspect value. Add 32 to swap left…
How to make fdisk -l display partition sizes by bytes instead of sectors? fdisk does not have such options as far as I know. However, good news is that you can use parted: # parted -l It will print partition info like # parted -l Model: Linux device-mapper (linear) (dm) Disk /dev/mapper/fedora_vm235-swap: 2164MB Sector size…
A commit is not the HEAD now. and git commit –amend will not work for it. How to change its commit message? You can use git rebase together with git commit –amend as follows. Assume your commit to be edited is 2b8ed. $ git rebase -i 2b8ed^ Change the pick to edit in the line…
I prefer Linux Mint (I am using Cinnamon) not automatically mounting a portable storage such as USB disk or iPhone for me and I would like do the mounting manually if I need it. The default behavior of Linux Mint is to automatically mount the disks. How to disable this? The auto mounting on Linux…
I want to add adsense ads to be shown to visitors on desktop only. How to remove AdSense ads for mobile devices? You can achieve this through using “Responsive ad unit” of AdSense. The support article Create a responsive ad unit from AdSense discusses this and gives an example. Check the “Hiding an ad unit”…
I want to attach a disk to a DomU. The Xen DomU is running and should not be rebooted. Hence, changing its configuration file is not an option. How to dynamically attach a disk to running DomU in Xen? To attach phy:vg_xen/vm-228-large to vm-228 as xvdb, run this on Dom0: # xl block-attach vm-228 phy:vg_xen/vm-228-large…