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Homework and Emergencies Homework & Coursework Questions Replace C instructions for system calls Post 302944405 by alwayslearn on Tuesday 19th of May 2015 07:06:07 AM
Old 05-19-2015
Replace C instructions for system calls

Use and complete the template provided. The entire template must be completed. If you don't, your post may be deleted!

1. The problem statement, all variables and given/known data:

Modify the program exec_in.c to obtain the same result but replacing the functions sleep and system for system calls. You can use exit, exec*, pause, alarm, etc. The new program will be called exec_in2.c and keep the original program syntax

2. Relevant commands, code, scripts, algorithms:

Code:
#include <stdlib.h>  
#include <stdio.h>  
#include <string.h>  
#include <errno.h>  
#include <unistd.h>   
#include "rutines.h"  

 int main(int argc, char *argv[])  
{      
      char cmd[256];
      int a;

      if (argc<2)
          Error("Insufficient arguments: exec_in <sec> <cmd> [args...]");

     sleep(atoi(argv[1]));
     cmd[0]='\0';

     for(a=2;a<argc;a++)
     {
          strcat(cmd,argv[a]);
          strcat(cmd," ");
      }

     system(cmd);
     exit(0);
}

3. The attempts at a solution (include all code and scripts):

I'm not sure what system call I need to solve the problem, I think that I need to use alarm but I don't know how to use correctly that, I never used system calls in C before, also I have only been using linux one week and I'm really lost.

4. Complete Name of School (University), City (State), Country, Name of Professor, and Course Number (Link to Course): Centre d'estudis Roca, Barcelona, Spain, Mariano Torres


Note: Without school/professor/course information, you will be banned if you post here! You must complete the entire template (not just parts of it).

I use ubuntu 12.04 64 bits

Last edited by alwayslearn; 05-19-2015 at 08:11 AM..
 

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isaexec(3C)						   Standard C Library Functions 					       isaexec(3C)

NAME
isaexec - invoke isa-specific executable SYNOPSIS
#include <unistd.h> int isaexec(const char *path, char *const argv[], char *const envp[]); DESCRIPTION
The isaexec() function takes the path specified as path and breaks it into directory and file name components. It enquires from the running system the list of supported instruction set architectures; see isalist(5). The function traverses the list for an executable file in named subdirectories of the original directory. When such a file is located, execve() is invoked with argv[] and envp[]. See exec(2). RETURN VALUES
If no file is located, isaexec() returns ENOENT. Other return values are the same as for execve(). EXAMPLES
Example 1: Example of isaexec() function. On a system whose isalist is sparcv7 sparc the program int main(int argc, char *argv[], char *envp[]) { return (isaexec("/bin/thing", argv, envp)); } will look first for an executable file named /bin/sparcv7/thing, then for an executable file named /bin/sparc/thing. It will invoke execve() on the first executable file it finds named thing. On that same system, a program called /u/bin/tofu can cause either /u/bin/sparcv7/tofu or /u/bin/sparc/tofu to be invoked using the follow- ing code: int main(int argc, char *argv[], char *envp[]) { return (isaexec(getexecname(), argv, envp)); } ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |MT-Level |Safe | +-----------------------------+-----------------------------+ |Interface Stability |Stable | +-----------------------------+-----------------------------+ SEE ALSO
exec(2), getexecname(3C), attributes(5), isalist(5) SunOS 5.10 20 Mar 1998 isaexec(3C)
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