You want to use the pmi tool from the powermanagement-interface package, e.g. to standby your Linux computer using the command line, but you get an error message like this:
Error org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.Hal was not provided by any .service files
You want to add a ssh key using ssh-add. It fails with this message:
Could not open a connection to your authentication agent.You own a Toshiba Notebook and want to set LCD backlight brightness using the commandline.
You are running a configure script on Linux. It exits with a message like this:
./configure: line 3638: LT_INIT: command not found
You want to get the IPv4 and/or IPv6 addresses of the local computer’s network interfaces using NodeJS in an OS-independent manner.
You encounter a GCC error message of the form
error: declaration of ... shadows a parameterYou encounter a GCC error message of the form
error: default argument for parameter of type <some type> has type <some other type>
Using fixed width integers is space-inefficient in many cases, especially if the majority of values are low and only use the less-significant bytes.
This guide describes the basics of varint (varying-length integer) encoding while focusing on C++ as programming language, but the basic concepts apply to any language.
Varint encodings use only the bytes that are needed to represent you integer value appropriately. A varint algorithm can represent the number 10 in only one byte while using 4 bytes to encode 800000000 (800 million). In many application this yields a significant overhead reduction since you would need to use larger integers if there is a slight change that your values grow beyond the boundary of the integer type that is applicable for the majority of your values. Additionally, you usually can only use 8,16,32 or 64 bit integers while 48 bit integers need to be coded manually in most languages. For example, if most of your values are between 0 and 100, but a few might be larger than 16384 (for unsigned integers), you would usually use a full 32-bit integer, even if most values could be represented by a single byte.
You have a large compressible read-only folder that eats up a lot of disk space. You want to compress it using SquashFS.
In C++ you want to check if a given file exists, but you can’t use stat() because your code needs to work cross-plaform.
You have installed zsh but you don’t see the menu-style autocompletion (where you can navigate the suggestions using the arrow keys on the keyboard)
In more recent Ubuntu Versions, the minimize, maximize and close icons have moved to the left upper corner of the window.
If you want them to show up on the right side instead, follow this guide:
gconftool-2 -s /apps/metacity/general/button_layout —type=string “menu:minimize,maximize,close”
The following small ANSI C99 program reads a String from stdin and prints out a Brainfuck program that prints the same String on stdout.
Compile using gcc -o bf bf.c
Use it like this:
cat my.txt | ./bf > my.bf
Source code:
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char** argv) {
unsigned char c;
unsigned char curval = 0;
//Initialize reg+1 with 8
while(1) {
c = getchar();
if(feof(stdin)) {break;}
while(curval != c) {
if(curval < c) {
putchar('+');
curval++;
} else if(curval > c) {
putchar('-');
curval--;
}
}
putchar('.');
}
}How does it work?
Basically it uses just one of the registers of the Brainfuck Turing machine and incremets or decrements the register to be able to print out the next byte. It doesn’t use any of the more ‘advanced’ features in Brainfuck like loops.
You are using adb sideload to communicate with your Android device (e.g. to flash the Nexus 4 using Clockworkmod recovery), but every time you try to execute `adb sideload` you get this error message:
error: closed
You want to setup gitlab using Apache and unicorn (no passenger!), but it doesn’t work, no matter how hard you try.
Update: Please also take a look at this followup article for an automatic compilation script that builds Ubuntu DEB packages!
You want to compile and install LevelDB (including development headers) on your Linux computer. ./configure && make && make install does not work so you don’t know how to do this.
or:
You have successfully compiled LevelDB, but make install doesn’t work (there is no official installation procedure yet) and you don’t know how to install it to your system
If you look at any SSE instruction table, you might notice that there are two basic types of operations:
For most operations, there are two versions, one packed and one scalar.
What’s the difference between them? It’s pretty simple:
SSE gains it performance from using packed operations implementing the SIMD paradigm (using a single instruction, multiple values are processed). However, it is occasionally useful to avoid expensive copying by using scalar operations operation on the SSE registers.
Also see the Original source
You have a video file and want to encode it to support all three HTML5 codecs currently available (WebM, Theora and H.264) on the majority of devices.
In the Linux shell, you have a file path and you want to strip everything but the filename, for example you have the path ../images/photo.jpg and want only photo.jpg