I have a shellscript that is having trouble finding a file. The text file exists so I don't understand what the issue is.   #!/bin/ksh goodmain $1 | sed -e '1,/mmxxaa/d'  $ ls -l total 1364 -rwxr-xr-x. 1 s student  94563 Apr 23 23:55 a.out -rwxrwxrwx. 1 s student     19 Apr 28 17:13 boo -rw-r--r--. 1 s student     89 Apr 24 00:58 cookies -rw-r--r--. 1 s student   1622 Dec  6 23:49 doc -rw-r--r--. 1 s student    148 Apr 23 16:14 textfile -rw-r--r--. 1 s student 597061 Apr 23 23:56 fn -rwxr-xr-x. 1 s student  94563 Apr 28 16:56 goodmain -rw-r--r--. 1 s student 427993 Apr 23 23:47 main.c -rw-r--r--. 1 s student 145256 Apr 24 00:40 main.o -rw-r--r--. 1 s student     72 Apr 28 16:53 makefile -rwxrwxrwx. 1 s student     46 Apr 28 17:24 p4 $ ./p4 textfile ./p4: line 2: goodmain: not found
Why do we use ./filename to execute a file in linux?  Why not just enter it like other commands gcc, ls etc...
What is attached to this spigot and how to remove Arduino Negative Voltage Reading with Positive Ground I am trying to measure voltage &amp; current off a solar charge controller from panel, battery &amp; load simultaneously with my arduino. I have managed to achieve this by tying all the negatives together and using it as GND, however, when I do that the charge controller doesn't function properly and when I switch to off-mode the loads still run. After checking the instruction manual further, I found out that the positives are shared common between Pan, Bat, Load. This was confirmed with a multimeter.   So now what I am thinking of doing is using the positive from the battery as the GND reference and then measuring all other voltages (through voltage dividers with respect to the GND). The voltages should then range between -17V to 0V.   However, I have read that the analog input pins are not able to read negative voltages, and with respect to the positive GND, the Analog inputs will all be negative.   EDIT: I was thinking of using an amplifier to invert positive ground to a negative ground, meaning I could measure all the positive sides of the voltages. But after getting answers from you guys it seems I may not have to use an amplifier and a voltage divider may suffice. I have currently included a 2 resistor voltage divider between each analog input, +5V source, Vmeasure which you can see in the diagram below.  According to my calculations, if this works, @-17V I should see 0.6V @ analog input. @0V I should see 4V at analog input.   I'd appreciate feedback on this circuit, and below in the second image I've also included a piece of another method suggested by @jonk (thanks), and would be interested in knowing what the benefits are of method B) over method A)  Thanks!  Ps. the ameters are there in place of ACS712 current sensors which also go into analog input pins.   Method A)        &ndash; Schematic created using   Method B (EDIT: This method has worked, I am still yet to test method A) thanks @Jonk)) Unfortunately hard disk of my system is damaged, now I recovered my database. But it cannot be attached again to SQL management studio 2005. The error is:  myfile.mdf is not a primary database file. (SQL server , error 5171) How do you get the logical xor of two variables in Python? Can a word be contracted twice (e.g. "I'ven't")? Prove that the derivative of an even differentiable function is odd, and the derivative of an odd is even. Reading order for Cosmere series by Brandon Sanderson My entry into Brandon Sanderson's works is Mistborn Trilogy, I finished and loved it. Then I got to know that many of his series are connected and happen in the same universe - Cosmere. Next I started with the Way of Kings, but am now kind of worried if I might read the series in the wrong order. So what is the right order to read them? is it the publication order..?   Elantris (2005)  Mistborn Trilogy Warbreaker (2009) The Stormlight Archive: The Way of Kings (2010) Mistborn: The Alloy of Law (2011) The Emperor's Soul (2012, novella) Shadows for Silence in the Forests of Hell (2013, short story published in Dangerous Women) The Stormlight Archive: Words of Radiance (2014)    or I have seen people suggest the following order too,   Mistborn Trilogy Elantris and the Emperor's Soul The Way of Kings Warbreaker Words of Radiance The Alloy of Law Shadows of Self   I have also read posts where they say it doesn't matter which order you read it in. So am confused, since I have already started the Way Of Kings (Only a few chapters in), should I stop it and go back to Elantris, and follow an order, or should I just continue finish this and pick other books in an order. Automatically login and lock Possibility of recovering files from a dd zero-filled hard disk I have "zero filled" (complete wiped) an external hard disk using dd, and from what I have heard: people said you should at least "zero fill" 3 times to be sure that the data are really wiped and no one can recover anything.  So I decided to scan the disk once again after I've zero filled the disk. I was expecting the disk to still have some random binary left. It turned out that it has only a few sequential bytes in the very beginning. This is probably the file structure type and other headers stuff. Other than that, it's all zeros and nothing else.  So if we have to recover any file from a zero filled disk, ...how? From what I've heard, even you zero fill the disk, you should still have some data left. ...or could dd really completely annihilate all data? let q be an odd prime and p a prime dividing $1+n+\dots+n^{q-1}$. Prove that $p = 1 \mod q$ or $p = q$.  I don't actually know how to start, i thought of using fermat's little theorem or an application of eulers formula, but it didn't really give me any insights.   Any hints? Design simulates perfectly but won't work on FPGA Strange Pop-up appldnld.apple.com:80 I received a strange Pop Up message. The unsettling part is password will be sent in clear text.  Is my phone affected with any malware or app virus ? How to add a confirm dialog to a command button? How would one prove that $$\lim_{n\rightarrow \infty} \frac{F_{n+1}}{F_n}=\frac{\sqrt{5}+1}{2}=\varphi$$  where $F_n$ is the nth Fibonacci number and $\varphi$ is the Golden Ratio? Problem  For what natural numbers is $n^3 &lt; 2^n$?  Attempt @ Solution   For $n=1$, $1 &lt; 2$ Suppose $n^3 &lt; 2^n$ for some $n = k \ge 1$ It looks like the inequality is true for $n = 0$, $n = 1$ and $n\ge10$ But, how can I prove this through induction? Is it possible to embed a scrollable frame inside a PDF? (This is an end-of-year crazy question)   Is it possible to embed a (scrollable) frame or a PDF inside a PDF? If so, how to do it in (pdf)LaTeX?  This is something pretty common in HTML (see for example ). Here it is a webpage with PDF frames   Here it is a fake screenshot so you get the idea.  Portable and non-portable (e.g. only-Acrobat) answers are welcomed.     Example of a down arrow below a frame. The up arrow can be on top of the frame and the triangles point up. I heard a lot about in-body image stabilization recently and I wonder how this technology works. I don't mean the mechanical part (I understand how the sensor moves along different axes to compensate), but the technique in principle:  When I take my 5D III and a lens like the 70-200 2.8 II IS USM with activated stabilization, the IS will constantly move one glas element within the lens in such a way that it directs the cone of light exactly onto the sensor, so that you can always use the full sensor area.  When the cone of light goes through an unstabilized lens and you need to move the sensor - how can it capture the same amount of light at all? The light enters the lens down a fixed axis right through the center of the lens. When the sensor currently moves down, for example, to compensate for a shake, I can't see how it then is still able to capture the full resolution? When a part of the sensor is below default/calm position, then there must be missing the same part on the opposite site?  There's only one way I could image IBIS to work without resolution reduction: if the sensor area was significantly bigger than the area exposed to light, so that there's still sensor available when it currently moves out of its initial position. But wouldn't this (partly) be the same as digital stabilization because the final image gets calculated from the full sensor area minus the not exposed area?  I really would like to understand this and it would be great if someone could "shed some light on this". Which is correct? - "Guess, what it is?" or "Guess, what is it?" I want to know which sentence is correct. If i say     Guess, what it is?   or     Guess, what is it?   which one is correct? How can I ask a person in which order in his family among the siblings? My colleague he have two brothers. I want to know, he is first/second/third son of his parents, ie., the order in the family among their siblings.  I can simply ask     Are you first son of your family?   It simply give some predictions, I don't want to that.  Is there a better way to ask the question? What's the simplest way to wrap extruded text around a cylinder? What's the simplest way to wrap extruded text around a cylinder that has a specific radius (for example, the label on a can of baked beans)?  I've tried using the Simple Deform modifier, but that (a) doesn't allow you to choose a radius and (b) requires the text to be converted to a curve.  I'm trying to model a cylinder with radius of 30, which has a line of embossed text that runs around the curved side, facing outward.  Thanks!