Using variables in system()

Afro · 07-02-2007, 06:35 AM

Is there some way to use variables in a system() command?

i've tried

Code:

system("%s",firstprogrampath);

but i only get an errormessage in the stdlib.h header (line 356), too many arguments in 'int system (const char*)'

as well in the actual program

(line 107) at this point in file.

So, is there any way to use variables in system();?

edit: also, firstprogrampath[50]; is a char variable. (string variable, i think the real name is?)

kris.c · 07-02-2007, 06:48 AM

Yes, it is possible to do so. Just pay attention to what the man pages say about the inputs that you can pass to the system command. For example, this code will display the contents of the file "test.c"

Code:

# include<stdio.h>
# include<stdlib.h>

int main()
{
 int num;
 const char abc[]="cat test.c";
 system(abc);
 return 0;
}

But, keep in mind that system() does make your code less portable

hk_mp5kpdw · 07-02-2007, 07:16 AM

If you must use system...

Use sprintf to create the command string.

Code:

char buffer[100];
char *firstprogrampath = "foo.exe";
int value = 10;

...

/* buffer will contain "foo.exe 10" */
sprintf(buffer,"%s %d",firstprogrampath, value);

/* Now call system */
system(buffer);

zacs7 · 07-02-2007, 07:18 AM

I think he means something along the lines of:

Code:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
	char command[BUFSIZ];
	char firstProgramPath[] = "test";

	sprintf(command, "%s", firstprogrampath);
	system(command);
	return 0;
}

edit: dang too late :@

Afro · 07-02-2007, 08:18 AM

Seeing as i got a few "If you have to use system..." then is there any other ways to execute a program from a variable?

The program is supposed to have a menu, with the options to add a program to the list, run a program from the list, remove a program from the list and save the list to the harddrive, all functions are yet to be implemented.

EDIT, also, here is the code (i am quite the newcomer so it is quite bulky, but it does what it should do atm).

Any tips or tricks on what could be improved are welcome.

Code:

/* A program written by Afro for users to add
and start various applications from a list */


/*  

TODO list 

-Switch-case main menu and sub menu if possible
-"Run the program" function 
-"delete latest program" function
-"exit" function -- DONE
-"save data" function
-Replace long IF-firstprogramexist with a function if possible
-Improve layout and add screen clearing
*/


/*------------------------------------------------------------------*/
/*----------------------- Headers ----------------------------------*/
/*------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>

/*------------------------------------------------------------------*/
/* ---------------------- Functions --------------------------------*/
/*------------------------------------------------------------------*/


/*------------------------------------------------------------------*/
/* -------------------- Menu Variables -----------------------------*/
/*------------------------------------------------------------------*/

int firstChoice;
int secondChoice;
int programnumber;

/*------------------------------------------------------------------*/
/*------------------- Program variables ----------------------------*/
/*------------------------------------------------------------------*/

/* First program */
char firstprogramname[30];
char firstprogrampath[50];
int firstprogramexist;

/* Second program */
char secondprogramname[30];
char secondprogrampath[50];
int secondprogramexist;

/*Third Program */
char thirdprogramname[30];
char thirdprogrampath[50];
int thirdprogramexist;

/*Fourth Program */
char fourthprogramname[30];
char fourthprogrampath[50];
int fourthprogramexist;

/*Fifth Program */
char fifthprogramname[30];
char fifthprogrampath[50];
int fifthprogramexist;

/*------------------------------------------------------------------*/
/* ---------------- End of the beginning ---------------------------*/
/*------------------------------------------------------------------*/

int main()
{
programnumber=1;

/* Print info about the program */
printf("This is a program-starter written by Afro\n");
printf("It has a maximum capacity of five stored programs\n");

/*------------------------------------------------------------------*/
/*----------------------- MAIN MENU --------------------------------*/
/*------------------------------------------------------------------*/

for(;;)
{
        printf("\nWhat do you want to do?\n\n");
        printf("Run a program (Enter 1)\n");
        printf("Show the programs in the list (Enter 2)\n");
        printf("Add a program to the list (enter 3)\n");
        printf("Delete the latest added program (enter 4)\n");
        printf("Exit (enter 5)\n\n");
        firstChoice=getchar();
        fflush(stdin);
        
/*------------------------------------------------------------------*/        
/*---------------------- Execute the programs ----------------------*/
/*------------------------------------------------------------------*/

    if (firstChoice==49)
    {
         printf("Enter the corresponding number \n");
         printf("of the program you want to run.\n");
         fflush(stdin);
         secondChoice=getchar();
         
         if(secondChoice==49)
         {
              printf("Running %s",firstprogramname);
              //system("%s",firstprogrampath);
         }
         else if(secondChoice==50)
              {
              printf("Running %s",secondprogramname);
              //system("");
              }
         else if(secondChoice==51)
              {
              printf("Running %s",thirdprogramname);
              //system("");
              }
         else if(secondChoice==52)
              {
              printf("Running %s",fourthprogramname);
              //system("");
              }
         else if(secondChoice==53)
              {
              printf("Running %s",fifthprogramname);
              //system("");
              }
         else
         {
                 printf("Please enter a correct number between 1-5.");
         }
    
}    //end of the run the program "if"    
/*------------------------------------------------------------------*/        
/*---------------------- List the programs -------------------------*/
/*------------------------------------------------------------------*/

    if (firstChoice==50)
    {
         printf("You wish to run a program\n");
         printf("These are the programs that the computer has stored:\n");
    
     
    if(firstprogramexist==1)
    {
                              printf("Number 1:\t %s \n",firstprogramname);
    }
    
    if(secondprogramexist==1)
    {
                              printf("Number 2:\t %s \n",secondprogramname);
    }
    
    if(thirdprogramexist==1)
    {
                              printf("Number 3:\t %s \n",thirdprogramname);
    }
    
    if(fourthprogramexist==1)
    {
                              printf("Number 4:\t %s \n",fourthprogramname);
    }
    
    if(fifthprogramexist==1)
    {
                              printf("Number 5:\t %s \n",fifthprogramname);
    }
    
    else printf("There are no programs in the list.\n");
} //end of the list the programs "IF"

/*------------------------------------------------------------------*/    
/*------------- The adding of the five possible programs -----------*/
/*------------------------------------------------------------------*/    

    else if (firstChoice==51 && programnumber==1)
    {
         printf("You wish to add a program\n");
         printf("Please enter the name of the program:\n\n");
         gets(firstprogramname);
         printf("\n\nPlease enter the path to the program:\n");
         fflush(stdin);
         gets(firstprogrampath);
         printf("The program will be shown as:\n %s\n\n",firstprogramname);
         printf("The path to the program is:\n %s\n\n",firstprogrampath);
         programnumber++;
         firstprogramexist=1;
    }
    
    else if (firstChoice==51 && programnumber==2)
    {
         printf("You wish to add a program\n");
         printf("Please enter the name of the program:\n\n");
         gets(secondprogramname);
         printf("\n\nPlease enter the path to the program:\n");
         fflush(stdin);
         gets(secondprogrampath);
         printf("The program will be shown as:\n %s\n\n",secondprogramname);
         printf("The path to the program is:\n %s\n\n",secondprogrampath);
         programnumber++;
         secondprogramexist=1;
    }
    
    else if (firstChoice==51 && programnumber==3)
    {
         printf("You wish to add a program\n");
         printf("Please enter the name of the program:\n\n");
         gets(thirdprogramname);
         printf("\n\nPlease enter the path to the program:\n");
         fflush(stdin);
         gets(thirdprogrampath);
         printf("The program will be shown as:\n %s\n\n",thirdprogramname);
         printf("The path to the program is:\n %s\n\n",thirdprogrampath);
         programnumber++;
         thirdprogramexist=1;
    }
    
    else if (firstChoice==51 && programnumber==4)
    {
         printf("You wish to add a program\n");
         printf("Please enter the name of the program:\n\n");
         gets(fourthprogramname);
         printf("\n\nPlease enter the path to the program:\n");
         fflush(stdin);
         gets(fourthprogrampath);
         printf("The program will be shown as:\n %s\n\n",fourthprogramname);
         printf("The path to the program is:\n %s\n\n",fourthprogrampath);
         programnumber++;
         fourthprogramexist=1;
    }
    
    else if (firstChoice==51 && programnumber==5)
    {
         printf("You wish to add a program\n");
         printf("Please enter the name of the program:\n\n");
         gets(fifthprogramname);
         printf("\n\nPlease enter the path to the program:\n");
         fflush(stdin);
         gets(fifthprogrampath);
         printf("The program will be shown as:\n %s\n\n",fifthprogramname);
         printf("The path to the program is:\n %s\n\n",fifthprogrampath);
         programnumber++;
         fifthprogramexist=1;
    }

/* Program-adding error (too many programs)*/
    else if (firstChoice==51 && programnumber>5)
    {
         printf("You have reached the maximum amount of programs");
    }

/*------------------------------------------------------------------*/    
/*----------------- END OF PROGRAM ADDING --------------------------*/
/*------------------------------------------------------------------*/    


/*------------------------------------------------------------------*/    
/*----------------- DELETE LATEST ADDED PROGRAM --------------------*/
/*------------------------------------------------------------------*/    


/*------------------------------------------------------------------*/    
/*--------------------------- EXIT ---------------------------------*/
/*------------------------------------------------------------------*/    

     else if (firstChoice==53)
     {
                         break;
     }

/*False Character error */    
    else 
    {
         printf("Enter a correct number.\n");
    }




}         // End of Loop

return(0);
}         // End of program

hk_mp5kpdw · 07-02-2007, 08:45 AM

Running a program from within another program is one of the topics in the FAQ.

Afro · 07-02-2007, 10:37 AM

Thanks guys, i got that part to work now.

dwks · 07-02-2007, 12:50 PM

Don't use fflush(stdin). http://faq.cprogramming.com/cgi-bin/...&id=1043284351
Don't use gets(). http://faq.cprogramming.com/cgi-bin/...&id=1043284351
Using character literals like '1' is much more readable than numbers like 49.
Rather than have firstprogram[], secondprogram[], etc, why not use a multidimensional array?
Code:
```
char programname[5][30];
```
Then you can get rid of all of that duplicate code.

brewbuck · 07-03-2007, 12:27 PM

Quote:

Originally Posted by Afro

Seeing as i got a few "If you have to use system..." then is there any other ways to execute a program from a variable?

Since you are designing a menu system, I see no reason why system() is not appropriate. Go ahead and use it. The other answers about using sprintf() to create the command string are the right info.

07-02-2007, 06:35 AM	#1
Afro Registered User Join Date: Jun 2007 Posts: 12	Using variables in system() Is there some way to use variables in a system() command? i've tried Code: system("%s",firstprogrampath); but i only get an errormessage in the stdlib.h header (line 356), too many arguments in 'int system (const char)' as well in the actual program (line 107) at this point in file. So, is there any way to use variables in system();? edit: also, firstprogrampath[50]; is a char variable. (string variable, i think the real name is?) Last edited by Afro; 07-02-2007 at 06:37 AM.*
Afro is offline

07-02-2007, 06:48 AM	#2
kris.c Eager young mind Join Date: Jun 2006 Posts: 338	Yes, it is possible to do so. Just pay attention to what the man pages say about the inputs that you can pass to the system command. For example, this code will display the contents of the file "test.c" Code: # include<stdio.h> # include<stdlib.h> int main() { int num; const char abc[]="cat test.c"; system(abc); return 0; } But, keep in mind that system() does make your code less portable __________________ In the middle of difficulty, lies opportunity
kris.c is offline

07-02-2007, 07:16 AM	#3
hk_mp5kpdw Registered User Join Date: Jan 2002 Location: Northern Virginia/Washington DC Metropolitan Area Posts: 2,787	If you must use system... Use sprintf to create the command string. Code: char buffer[100]; char firstprogrampath = "foo.exe"; int value = 10; ... / buffer will contain "foo.exe 10" / sprintf(buffer,"%s %d",firstprogrampath, value); / Now call system */ system(buffer); __________________ On two occasions I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question. --Charles Babbage, 1792-1871 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
hk_mp5kpdw is offline

07-02-2007, 07:18 AM	#4
zacs7 Woof, woof! Join Date: Mar 2007 Location: Australia Posts: 3,139	I think he means something along the lines of: Code: #include <stdio.h> #include <stdlib.h> int main(void) { char command[BUFSIZ]; char firstProgramPath[] = "test"; sprintf(command, "%s", firstprogrampath); system(command); return 0; } edit: dang too late :@ __________________ "I.T. gets the chicky-babes" - M. Kelly bakefile \| vim
zacs7 is offline

07-02-2007, 08:45 AM	#6
hk_mp5kpdw Registered User Join Date: Jan 2002 Location: Northern Virginia/Washington DC Metropolitan Area Posts: 2,787	Running a program from within another program is one of the topics in the FAQ. __________________ On two occasions I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question. --Charles Babbage, 1792-1871 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
hk_mp5kpdw is offline

07-02-2007, 10:37 AM	#7
Afro Registered User Join Date: Jun 2007 Posts: 12	Thanks guys, i got that part to work now.
Afro is offline

07-02-2007, 12:50 PM	#8
dwks Frequently Quite Prolix Join Date: Apr 2005 Location: Canada Posts: 7,629	Don't use fflush(stdin). http://faq.cprogramming.com/cgi-bin/...&id=1043284351 Don't use gets(). http://faq.cprogramming.com/cgi-bin/...&id=1043284351 Using character literals like '1' is much more readable than numbers like 49. Rather than have firstprogram[], secondprogram[], etc, why not use a multidimensional array? Code: char programname[5][30]; Then you can get rid of all of that duplicate code. __________________ dwk Seek and ye shall find. quaere et invenies. "Simplicity does not precede complexity, but follows it." -- Alan Perlis "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra "The only real mistake is the one from which we learn nothing." -- John Powell Other boards: DaniWeb, TPS Unofficial Wiki FAQ: cpwiki.sf.net My website: http://dwks.theprogrammingsite.com/ Projects: codeform, xuni, atlantis, etc. New project: nort
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