Calling system with a string variable

Can a call to system be string variable or actual string in double quoted form?

Code:

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            sprintf(cmd, "cp %d.txt %d.csv",i,i);
        pid_err=system(cmd); //Problem here: it's printing garbage on the screen

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Quote:

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Originally Posted by 911help

Can a call to system be string variable or actual string in double quoted form?

Code:

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        sprintf(cmd, "cp %d.txt %d.csv",i,i);
    pid_err=system(cmd); //Problem here: it's printing garbage on the screen

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>Can a call to system be string variable or actual string in double quoted form?
Either of them is acceptable. Fo instance

Code:

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char str[] = "clear";
system(str);
or
system("clear");

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>Problem here: it's printing garbage on the screen
If the return value was other than 0 then the system function failed.

ssharish

I am using gdb to walk through the break points.

printf("print before system(cmd) call\n");
pid_err=system(cmd); //Problem here: it's printing garbage on the screen
printf("print after system(cmd) call\n");

Soon as I call system(cmd), garbage is printed out on the screen. why?

sample output:

Quote:

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��ႇ
.x��ႇ
.x��ႇ
.x��ႇ
�<\�p��<\�p�

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Check the system() return value and see if your system call was successful.

Code:

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if( system("clear") )
{
    printf( " Error " );
    return 1;
}
else
  printf( " < Message > " );

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ssharish

I don't know what the problem here. I tried to gzip the file using system(). Text file is there, but never get gzipped. I get garbage printed out on the console soon as I call system();.

Do I have to have root access on the linux shell to be able to call system? Does
sprintf(cmd, "gzip -c ./data_id_%d.txt",i); put a '\0' in cmd, after placing the string "gzip -c ./data_id_%d.txt"?

server.conf:

Code:

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num_of_files=3;

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file_temp.c:

Code:

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#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

#define SIZE 256

FILE *configfile;
int  num_files;
char conf[100];
char *buffer;

char cmd[SIZE];

int main (int argc, char *argv[])
{
int i=0;
        configfile= fopen("./server.conf", "r");
        fgets(conf,100, configfile);
        fclose(configfile);
    buffer=strtok(conf,";");
    strtok(buffer,"=");
    num_files=atoi(strtok(NULL,"="));
    sprintf(cmd, "gzip -c ./data_id_%d.txt",i);
    printf("system(%s)\n", cmd);
    if( system(cmd) )
    {
            printf( " Error \n" );
            return 1;
    }
    else
            printf( " < System call success > \n" );
    printf("After the system call\n");
   
    exit (0);
}

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Here is my gdb output.

Code:

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****printted whole bunch of garbage here.********* and then stuff below*********
System call has success >

Breakpoint 2, main () at file_temp.c:34
34          printf("After the system call\n");
(gdb) continue
Continuing.
After the system call

Program exited normally.

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Is this you as well?
http://www.daniweb.com/forums/thread101796.html

Salem, I tried fork as you mentioned on Daniweb. It gave a problem. I wanted to try system call. This is also giving me problems.

Can someone help with this? No one had done zipping stuff from system call?

Anything else I need to do, i.e setuid?

Quote:

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Originally Posted by 911help

****printted whole bunch of garbage here.********* and then stuff below*********

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The "garbage" is undoubtedly the output of gzip -c. (With the -c flag, gzip sends output to stdout.)

D

million thanks for everyone.