Programming :: Calling System Calls In C Runtime (in The Run-time)?
Sep 23, 2010
I know there is a way to call winapi in runtime in windows. I want to ask how can I call a system call in gcc in runtime (when I don't know what it can be)? I don't mean syscall that I think is for calling only system calls and not library functions.
How does a C program start in linux? Is main() the first function called in the a c application by kernel. I understand it is the first called function written by the application programmer, but the question is to understand the what all kernel does and what all functions it calls before calling main()
What is the real difference between system calls and normal function calls. Ultimately function calls too would be passed to kernel for some or the other work.
I'm trying to call a system command in perl and am having an issue with it.
Here's an example of a command i'd like to call: Code: sed -i '4 c192.168.1.4 www.something.com' hosts this is the section in my perl script where I create the variable and call it: Code: $doit = `sed -i '$line c$ip $host hosts'`system($doit); The $line, $ip, and $host variables are working fine becasue I can replace that section with "prints" and they come out fine. I imagine the problem is where I am creating the $doit variable.
I'm trying to produce a alphabetic, non-repetitive list of all System service calls in all c files located in a folder. Here's what I got so far. grep -ow '[A-Za-z]*SYS[$][A-Za-z]*' *.c | sort Which produces all system service calls in alphabetic order I just need to find out how to make it non-repetitive.
I am working with fedora 6 , i386 architecture.I am trying to write on keyboard port via program.On inspation i come to know that 0x0060 to 0xz006f are used for keyboard in linux 2.6 kernel in the i/o space from kernel.
I am trying to install the Matlab 7.5 compiled runtime for 64-bit Linux (MCRInstaller.75.glnxa64.bin) and keep getting a "No Java Runtime Environment(JRE) was found on this system." error message.
I understand the JRE is bundled with MCRInstaller and will self-compile/install. However, I don't have admin access, could this be the source of the problem? If so, how could I fix it (not sure how to direct it to install locally without going into the source code)?
I got around this error before, but stupid me didn't write down what I did and I forgot.
when i call the "system()" function from my C program everything works well, but when i try to call it from a cgi C program it doesn't work. the server log tells me this is a permission error.i have chmod'ed 755 the cgi program but it still does not work.
I've searched for ways to do this with cron and come up empty. I want to schedule the update manager downloads for the 2-7am hours to avoid being penalized by my satellite service provider for excessive downloads. No, I can't change providers as I live in a rural area where it's the only relatively high speed option
I am new to both linux and fortran programming. I am trying to read from an external file, but it gives this error message: Fortran runtime error: Bad integer for item 1 in list input Part of the code that has the problem is:
All the variables have been declared before and there is no problem with that. The problem (error message) is in the (first) line that deals with open(unit=3,file='..//').
I'm writing an application with a plugin architecture and would like modify (specifically add to) the dynamic library search path while the main executable is running.
The plugin paths are not known until the application is running so I can't set LD_LIBRARY_PATH ahead of time.
My understanding (although I haven't tested it) is that the executable will only parse the LD_LIBRARY_PATH once, early on, so modifying this environment variable at runtime will have no effect.
(Note - on Windows the solution is to modify the PATH environment variable)
I know it's possible to specify the full path to load a dynamic library, and this would work if the plugin(s) only had a single library to load, but some of them will have a bunch of libraries with their own inter-dependencies, so I'd like the plugin folder(s) to get added to the search path to pick up the dependant libs.
I have a question about calling an asm function from C....It doesn't work unless I create an asm variable to hold the value of the function in....Why?Here's the code that doesn't work...
asmfile.s - version one Code: .section .data mydata: .ascii "this is the message! .equ mylen, . - mydata
I am doing a web site program and what I need is to call a C program in the PHP cloud.Do u think it would be possible? The web site would get the user input from PHP UI and pass to the C program , the C program would process the function with the user input and output the a PHP page.
I've been receiving a ton of calls from telemarketers and political callcenters. What would be the simplest way to use Ubuntu to automatically drop calls incoming from blacklisted numbers?
I have Comcast Digital Voice service, which is technically VOIP but I think it interfaces with modems themselves just like any other phone service would. I have a dedicated Ubuntu server sitting next to a phone jack already, so I'd like to use that if possible.
I've seen FreePBX and Asterisk, and hear that they can do the job. However, I haven't been able to tell just how easily they could be set up. It sounds like they might require me to get rid of all my phones and use soft phones instead... Does anybody know if it is as simple as buying a voice modem and configuring a PBX software to interface with it?
I've implemented a few custom system calls in my Ubuntu kernel, but I'm having some issues with the return values. Each function returns a variety of non-negative integers depending on which error is encountered. However, when I'm testing the system calls, the only negative value that gets returned to the user program is -1, regardless of what I have in the code.
Is there some special path I have to take to get the proper return values?
I would like to trace a user's activity by monitoring system calls. Is there a way to use strace such that at startup it will begin tracing all system calls? Or is there any other method to automatically trace the system calls used during a user's session automatically without having to call strace manually?
I'm new to C language and some help finding places in the following code where a system call is made and error checking is not done. I found one but since I don't know C language at all I'm not exactly sure what else to look for. Link to my file: [URL]...
I found one and added error checking: if (setoutpipe){ //Changes: Added error checking to the system call close() //Orginal Code: close(pidefd[1]); if(close(pipefd[1] != 0){ fprintf(stderr, "Could not close piple. "); exit(255); }
I want to call c exe from java source code and i want to interact with the c program during it's execution, i am able to send the parameters to c program but i am not able to interact with it.
I have spent quite a lot of time on this problem. It seems like the file is sometimes closed when reaching config(fd), but removing the usleep(a while) seems to remove the problem.
I have a bash script that changes the iptables.Now i call this bash script in my php code.When this bash script is running the part of code that contains iptables instruction is not running because we need to be in superuser mode(root)
I'm trying to call some Fortran 95 code in C, but I'm having problems with integers not having the same value in C as in Fortran, and changing values upon each run of the program. I think it has to do with the integer type, but I don't know how to fix it. I'm running Gentoo x86. Here are the files I've got: