Question

im trying to concatsomm strings and call a expext script on my server, but im a .net programer and new to c and pointers so keep messing up… what am i doing wrong here?

or a better question wold be how should i really do this?

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

int main(int argc, char *argv[])
{
    //location of expect script that ssh and gets info on other server
    char str0[] = "./home/systemio/Develop/getfile ";

    char* strP =  argv[1];
    char str1 = (char)*strP;
    char str2[] = " > file.txt";

    strcat(str0,str1);

    strcat(str0,str2);

    printf("%s\n", str0);
    system(str0);

    printf("Done!!!!\n");
    return 0;
}

Answer 1

You can allocate a buffer for the system command to ensure there is definitely enough space to construct the full command:

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

int main(int argc, char* argv[])
{
    /* Ensure 1 argument supplied. */
    if (2 == argc)
    {
        /* malloc()ing the system command buffer means you can safely
           edit 'util' and 'output' without being concerned about the
           size of an array.
           The '+2' is for the char from argv[1]
           and for the terminating null character. */
        const char* util   = "./home/systemio/Develop/getfile ";
        const char* output = " > file.txt";
        char* str0         = malloc(strlen(util) + strlen(output) + 2);

        if (str0)
        {
            if (sprintf(str0, "%s%c%s", util, *argv[1], output) > 0)
            {
                printf("%s\n", str0);
                system(str0);
                printf("Done!!!!\n");
            }

            /* free() malloced memory. */
            free(str0);
        }
    }

    return 0;
}