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  • Why do C compilers prepend underscores to external names?

    - by Michael Burr
    I've been working in C for so long that the fact that compilers typically add an underscore to the start of an extern is just understood... However, another SO question today got me wondering about the real reason why the underscore is added. A wikipedia article claims that a reason is: It was common practice for C compilers to prepend a leading underscore to all external scope program identifiers to avert clashes with contributions from runtime language support I think there's at least a kernel of truth to this, but also it seems to no really answer the question, since if the underscore is added to all externs it won't help much with preventing clashes. Does anyone have good information on the rationale for the leading underscore? Is the added underscore part of the reason that the Unix creat() system call doesn't end with an 'e'? I've heard that early linkers on some platforms had a limit of 6 characters for names. If that's the case, then prepending an underscore to external names would seem to be a downright crazy idea (now I only have 5 characters to play with...).

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  • Why is the software world full of status codes?

    - by David V McKay
    Why did programmers ever start using status codes? I mean, I guess I could imagine this might be useful back in the days when a text string was an expensive resource. WAYYY back then. But even after we had megabytes of memory to work with, we continued to use them. What possible advantage could there be for obfuscating the meaning of an error message or status message behind a status code?

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  • Unwanted Shell expansion when assigning the output of a shell command to a variable

    - by Rob Goodwin
    I am exporting a portion of a local prototypte svn repository to import into a different repo. We have a number of svn properties set throughout the repo so I figured I would write a script to list the file elements and their corresponding properties. How hard can that be right. So I write started writing a bash script that would assign the output of the svn proplist -v to a variable so I could check if the specified file had any properties. #!/bin/bash svn proplist -v $1 o=$(svn proplist -v "$1") echo $o now this works fine and echos the output of the svn proplist command. But if the proplist command returns something like svn:ignore : * build it performs a shell expansion on the * and inserts the entire directory listing prior to the build property value. So if the directory had a.txt, b.txt and build files/dirs in it, the output would look like. svn:ignore a.txt b.txt build I figure I need to somehow escape the output or something to keep the expansion from happening, but have yet to find something that works. There are other ways to do this, but I hate when I cannot figure something out. and I have to admin, I think this one beat me ( well given the time I can spend on it )

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  • Launch command on remote Windows machine, given admin credentials

    - by Bilal Aslam
    I have a Windows Server 2008 instance on Amazon EC2 (Amazon's cloud compute platform, which provides VMs in the cloud). It has an external IP, and I have an admin account on the box. I would like to 'bootstrap' this instance remotely i.e. I want to run commands to download, install and configure apps on it, all without having to log on even once. I have figured out how to do this to a remote, domain-joined computer using WMI. I can even use psexec to get what I want, as long as the remote computer is part of the domain. However, I have NOT been able to do for a remote computer on EC2. Here are some specific restrictions: 1) The remote computer is not part of my domain, hence no Kerberos 2) The remote computer does not have a cert I trust, or vice versa I am sure I am running into to some auth/trust restriction. Is there any way I can run a single command on the remote, given that I have admin privileges? I'm not tied down to using WMI, but I do need to run a command somehow. Feels like this should be a solved problem.

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  • Show last command with up arrow on a linux c shell

    - by nunos
    I have implemented a simple linux shell in c. Now, I am adding some features and one I immediately thought about was to be able to show the last commands with the up arrow. Question 1: However, I have no idea how to accomplish this. Do you? Question 2: Any comment on how to store the "history" commands are also appreciated. I suppose something like a queue which allows access to all elements would be a good idea. Am I wrong? Do I have to implement it or is there already some good implementation out there I should know about? Thanks.

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  • I trying to backreference using the sed command

    - by Paul
    I am relative new to shell scripting and sed. I need to substitute a pattern, globably, but I also need to remember (or save) part of the pattern and use it later in the same substitute command. The saved pattern will be varible, so I need to use a wild card. For example, input message=trt:GetAudioSourcesRequest/> and I want to end up with something like input message=trt:GetAudioSourcesRequest PAUL/GetAudioSourcesRequest/> but the function string "GetAudioSourcesRequest" will change (in length also) throughtout the file, so I need a wild card, e.g. sed -i "s/input message=trt:<wild card in here>/>/input message=trt:<print wild card> PAUL/<print wild card>/> I have managed to get the following command to nearly do what I want but it is too rigid. It only stores a 4 syllable pattern so if I have a function name such as GetProfileRequest, this doesn't work echo "input message=\"trt:GetAudioSourcesRequest\"/>" | sed 's/input message=\"trt:\([A-Z][a-z]*\)\([A-Z][a-z]*\)\([A-Z][a-z]*\)\([A-Z][a-z]*\).*/input message=\"trt:\1\2\3\4\ PAUL\/\1\2\3\4"\/\>/g' This outputs input message="trt:GetAudioSourcesRequest PAUL/GetAudioSourcesRequest"/> Which is ok but when I use GetProfileRequest this doesn't. I have come accross \W and [^[:alnum:]] or [[:alnum:]] but I don't how to use them Thanks in advance.

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  • Why has anybody ever used COBOL?

    - by sarzl
    I know: You and me hate COBOL. I took a look at a lot of code examples and it didn't take me long to know why everybody tries to avoid it. So I really have no idea: Why was COBOL ever used? I mean: Hey - there was Fortran before it, and Fortran looks like a jesus-language compared to COBOL. This isn't argumentative but historical as I'm young and didn't even know about COBOL before 4 months.

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  • Cobol: science and fiction

    - by user847
    There are a few threads about the relevance of the Cobol programming language on this forum, e.g. this thread links to a collection of them. What I am interested in here is a frequently repeated claim based on a study by Gartner from 1997: that there were around 200 billion lines of code in active use at that time! I would like to ask some questions to verify or falsify a couple of related points. My goal is to understand if this statement has any truth to it or if it is totally unrealistic. I apologize in advance for being a little verbose in presenting my line of thought and my own opinion on the things I am not sure about, but I think it might help to put things in context and thus highlight any wrong assumptions and conclusions I have made. Sometimes, the "200 billion lines" number is accompanied by the added claim that this corresponded to 80% of all programming code in any language in active use. Other times, the 80% merely refer to so-called "business code" (or some other vague phrase hinting that the reader is not to count mainstream software, embedded systems or anything else where Cobol is practically non-existent). In the following I assume that the code does not include double-counting of multiple installations of the same software (since that is cheating!). In particular in the time prior to the y2k problem, it has been noted that a lot of Cobol code is already 20 to 30 years old. That would mean it was written in the late 60ies and 70ies. At that time, the market leader was IBM with the IBM/370 mainframe. IBM has put up a historical announcement on his website quoting prices and availability. According to the sheet, prices are about one million dollars for machines with up to half a megabyte of memory. Question 1: How many mainframes have actually been sold? I have not found any numbers for those times; the latest numbers are for the year 2000, again by Gartner. :^( I would guess that the actual number is in the hundreds or the low thousands; if the market size was 50 billion in 2000 and the market has grown exponentially like any other technology, it might have been merely a few billions back in 1970. Since the IBM/370 was sold for twenty years, twenty times a few thousand will result in a couple of ten-thousands of machines (and that is pretty optimistic)! Question 2: How large were the programs in lines of code? I don't know how many bytes of machine code result from one line of source code on that architecture. But since the IBM/370 was a 32-bit machine, any address access must have used 4 bytes plus instruction (2, maybe 3 bytes for that?). If you count in operating system and data for the program, how many lines of code would have fit into the main memory of half a megabyte? Question 3: Was there no standard software? Did every single machine sold run a unique hand-coded system without any standard software? Seriously, even if every machine was programmed from scratch without any reuse of legacy code (wait ... didn't that violate one of the claims we started from to begin with???) we might have O(50,000 l.o.c./machine) * O(20,000 machines) = O(1,000,000,000 l.o.c.). That is still far, far, far away from 200 billion! Am I missing something obvious here? Question 4: How many programmers did we need to write 200 billion lines of code? I am really not sure about this one, but if we take an average of 10 l.o.c. per day, we would need 55 million man-years to achieve this! In the time-frame of 20 to 30 years this would mean that there must have existed two to three million programmers constantly writing, testing, debugging and documenting code. That would be about as many programmers as we have in China today, wouldn't it? Question 5: What about the competition? So far, I have come up with two things here: 1) IBM had their own programming language, PL/I. Above I have assumed that the majority of code has been written exclusively using Cobol. However, all other things being equal I wonder if IBM marketing had really pushed their own development off the market in favor of Cobol on their machines. Was there really no relevant code base of PL/I? 2) Sometimes (also on this board in the thread quoted above) I come across the claim that the "200 billion lines of code" are simply invisible to anybody outside of "governments, banks ..." (and whatnot). Actually, the DoD had funded their own language in order to increase cost effectiveness and reduce the proliferation of programming language. This lead to their use of Ada. Would they really worry about having so many different programming languages if they had predominantly used Cobol? If there was any language running on "government and military" systems outside the perception of mainstream computing, wouldn't that language be Ada? I hope someone can point out any flaws in my assumptions and/or conclusions and shed some light on whether the above claim has any truth to it or not.

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  • Why is RAISERROR misspelled? Or is it not?

    - by Jason
    Why isn't RAISERROR spelled RAISEERROR? Where is the second E? I could understand if it were some ancient keyword length constraint, but I wouldn't expect it to be a nine-character limit. Is RAIS or RROR a technical word such that "raise-error" is just a mis-reading? Are its (immediate) origins in a different language? I've searched Google but not finding much on the subject.

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  • Heroku: bash: bundle: command not found

    - by Space Monkey
    My heroku deployment is crashing with following errors. 2012-12-12T17:16:18+00:00 app[web.1]: bash: bundle: command not found 2012-12-12T17:16:19+00:00 heroku[web.1]: Process exited with status 127 2012-12-12T17:16:19+00:00 heroku[web.1]: State changed from starting to crashed The Heroku documentation for this error is to set PATH and GEM variables as described in https://devcenter.heroku.com/articles/changing-ruby-version-breaks-path I tried that, however that too is not helping. ? heroku config:add PATH=bin:vendor/bundle/ruby/1.9.1/bin:/usr/local/bin:/usr/bin:/bin ? heroku config:add GEM_PATH=vendor/bundle/ruby/1.9.1 ? heroku run rake db:migrate Running rake db:migrate attached to terminal... up, run.7130 bash: bundle: command not found Next, I tried setting Ruby version in my Heroku app. This increased the slugsize. But app was still not up. Gemfile ruby "1.9.2" Pushed to Heroku -----> Using Ruby version: ruby-1.9.2 -----> Installing dependencies using Bundler version 1.2.2 heroku run "ruby -v" Running `ruby -v` attached to terminal... up, run.4483 ruby 1.9.2p320 (2012-04-20 revision 35421) [x86_64-linux] Can someone please advice

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  • (For what) Are Fortran, Cobol and Co. used today?

    - by lamas
    I'm a relatively young programmer and so I don't really know much about languages like Fortran or Cobol that have their origins in the beginning of modern informatics. I'm a bit confused because it seems like there are many people out there saying that these two languages are still very alive and being used all over the world whereas others say the opposite. In addition, it seems like there are only very few questions tagged Fortran or Cobol here on stackoverflow. Can someone "demystify" the situation for me? Who uses these senior languages these days and are they even used anymore? Do you have any experiences with one of the languages or do you know something about their latest developments?

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  • What is the purpose of Java's unary plus operator?

    - by Syntactic
    Java's unary plus operator appears to have come over from C, via C++. As near as I can tell, it has the following effects: promotes its operand to int, if it's not already an int or wider unboxes its operand, if it's a wrapper object complicates slightly the parsing of evil expressions containing large numbers of consecutive plus signs It seems to me that there are better (or, at least, clearer) ways to do all of these things. In this SO question, concerning the counterpart operator in C#, someone said that "It's there to be overloaded if you feel the need." But in Java, one cannot overload any operator. So does this operator exist in Java just because it existed in C++?

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  • What does IUrlHistoryStg::BindToObject Method do ?

    - by BHOdevelopper
    I'm looking for a way to access the address bar search so that i can append some personnal url at the end of the current list, and i found 'IUrlHistoryStg::BindToObject' but there is no documention linked to it. Anyone knows what this method does ? On msdn: http://msdn.microsoft.com/en-us/library/aa767718%28VS.85%29.aspx

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  • What inspired WPF?

    - by Andrei Rinea
    I was told by someon that, just as .NET started inspired from Java, WPF was inspired by a similar technology, as "Microsoft never innovates". However, I can't find anything remotely close to WPF. What particular technology did or could have inspired Microsoft to write WPF?

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  • LaTex: how does the include-command work?

    - by HH
    I supposed the include-command copy-pastes code in the compilation, it is wrong because the code stopped working. Please, see the middle part in the code. I only copy-pasted the code to the file and added the include-command. $ cat results/frames.tex 10.31 & 8.50 & 7.40 \\ 10.34 & 8.53 & 7.81 \\ 8.22 & 8.62 & 7.78 \\ 10.16 & 8.53 & 7.44 \\ 10.41 & 8.38 & 7.63 \\ 10.38 & 8.57 & 8.03 \\ 10.13 & 8.66 & 7.41 \\ 8.50 & 8.60 & 7.15 \\ 10.41 & 8.63 & 7.21 \\ 8.53 & 8.53 & 7.12 \\ Latex code \begin{table} \begin{tabular}{ | l | m | r |} \hline $t$ / s & $d_{1}$ / s & $d_{2}$ / s \\ $\Delta h = 0,01 s$ & $\Delta d = 0,01 s$ & $\Delta d = 0,01 s$ \\ \hline % I JUST COPIED THE CODE from here to the file, included. % It stopped working, why? \include{results/frames.tex} \hline $\pi (\frac{d_{1}}{2} - \frac{d_{2}}{2})$ & $2 \pi R h$ & $2 \pi r h$ \\ \hline \end{tabular} \end{table}

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  • Is there any kind of standard for 8086 multiprocessing?

    - by Earlz
    Back when I made an 8086 emulator I noticed that there was the LOCK prefix intended for synchonization in a multiprocessor environment. Yet the only multitasking I know of for the x86 arch. involves use of the APIC which didn't come around until either the Pentiums or 486s. Was there any kind of standard for 8086 multitasking or was it done by some manufacturer specific extensions to the instruction set and/or special ports? By standard, I mean things like: How do you separate the 2 processors if they both use the same memory? This is impossible without some kind of way to make each processor execute a different piece of code. (or cause an interrupt on only one processor)

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  • Popen is no able to process a command that runs in shell

    - by IceMan85
    Hello everybody, I have already read the previous questions posted on the same argument but I really haven't figured it out yet. I am trying to run a command that works without issues from the command line : xyz@klm:~/python-remoteWorkspace/PyLogParser/src:18:43ush -o PPP -p PRD -n log 'pwd' 6:43PM PPP:prd:lgsprdppp:/ama/log/PRD/ppp but when I do the same in python I always get errors : stringa = Popen(["ush -o PPP -p PRD -n log 'pwd'"], stdout=PIPE, stdin=PIPE).communicate()[0] Here the error. Traceback (most recent call last): File "getStatData.py", line 134, in retrieveListOfFiles(infoToRetList) File "getStatData.py", line 120, in retrieveListOfFiles stringa = Popen(["ush -o PPP -p PRD -n log 'pwd'"], stdout=PIPE, stdin=PIPE).communicate()[0] File "/opt/python-2.6-64/lib/python2.6/subprocess.py", line 595, in init errread, errwrite) File "/opt/python-2.6-64/lib/python2.6/subprocess.py", line 1092, in _execute_child raise child_exception OSError: [Errno 2] No such file or directory I've tried also different solutions like stringa = Popen(["ush", "-o", "PPP", "-p" "PRD", "-n", "log", '"pwd"'], stdout=PIPE, stdin=PIPE).communicate()[0] but nothing seems to work. I have also tried to put the absolute path to ush but nothing... Can somebody please explain me what am I doing wrong ? Thanks in advance, AM.

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  • Where are the new ideas in programming languages?

    - by 0xF
    I've recently been looking into the topic of programming languages and from what I've seen, few to none serious languages try making really "new" things that were not seen before their creation. Why do all more or less successful programming languages since 1980 or so just combine aspects of their predecessors? I just can't believe that programming languages "can't get any better"..

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  • What was the single byte change to port WordStar from CP/M to DOS?

    - by amarillion
    I was re-reading Joel's Strategy Letter II: Chicken and Egg problems and came across this fun quote: In fact, WordStar was ported to DOS by changing one single byte in the code. (Real Programmers can tell you what that byte was, I've long since forgotten). I couldn't find any other references to this with a quick Google search. Is this true or just a figure of speech? In the interest of my quest to become a "Real Programmer", what was the single byte change?

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  • Why does C's "fopen" take a "const char *" as its second argument?

    - by Chris Cooper
    It has always struck me as strange that the C function "fopen" takes a "const char *" as the second argument. I would think it would be easier to both read your code and implement the library's code if there were bit masks defined in stdio.h, like "IO_READ" and such, so you could do things like: FILE* myFile = fopen("file.txt", IO_READ & IO_WRITE); Is there a programmatic reason for the way it actually is, or is it just historic? (i.e. "That's just the way it is.")

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  • What does the 'X' in .aspx, docx, xlsx, etc... represent?

    - by Serapth
    It's one of those things you just take for granted until one day someone asks you and you realize you can't answer it. Much like for years I never questioned the use of 1033 directories in Microsoft products for years until one day, someone asked me about it. Around the release of .NET and Office 2007, Microsoft added an x to basically all of their extensions and I frankly took it as representing XML, but that simply doesn't make sense with .aspx. So, I realize this is a very non technical question, but now that the question has been asked of me and my googling hasn't given me an answer, can anyone tell me with authority what the X represents? Is it extended? Xml? Or is there no meaning behind it?

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  • Gem Load Error about whois command and removed cache

    - by Puru puru rin..
    Hello, I have an awesome trouble with Gem. After executing this command: rm -f /usr/local/lib/ruby/gems/1.9.1/cache/* I can not do any thing. If I try for instance: gem cleanup I get this kind of answer: /usr/local/lib/ruby/gems/1.9.1/gems/gemwhois-0.1/lib/gemwhois.rb:3:in `require': no such file to load -- rubygems/commands/whois (LoadError) from /usr/local/lib/ruby/gems/1.9.1/gems/gemwhois-0.1/lib/gemwhois.rb:3:in `<top (required)>' from /usr/local/lib/ruby/gems/1.9.1/gems/gemwhois-0.1/lib/rubygems_plugin.rb:2:in `require' from /usr/local/lib/ruby/gems/1.9.1/gems/gemwhois-0.1/lib/rubygems_plugin.rb:2:in `<top (required)>' from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1113:in `load' from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1113:in `block in <top (required)>' from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1105:in `each' from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1105:in `<top (required)>' from <internal:gem_prelude>:235:in `require' from <internal:gem_prelude>:235:in `load_full_rubygems_library' from <internal:gem_prelude>:334:in `const_missing' from /usr/local/bin/gem:12:in `<main>' It's the same for gem -v, of just gem command... I'm working of Snow Leopard. What should the best solution about you? Thanks a lot!

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