capturing empty output returned from commandline and display some message if its empty

Question

Thank you guys for answering "capturing commandline output directly in a buffer" .. thanks a lot.. I used popen() to get my results correct.

here i have one more thing may be small one

I need to print something in my window when the script "check.sh" returns nothing, means validation when no output from the script is returned.

check.sh contains nothing in it.. simply a blank sh file returns nothing when executed.I am testing with empty sh file.(I cannot show u the exact script that is why)

what i want to print is some message like "configure some thing" through C when check.sh returns nothing.

I checked buffer line(check in the module below) with "\n","\r","\0",NULL.. I donno what it is taking when the script returns nothing

I ll be calling the module as execute_command("sh check.sh")

Here is my module

  char *execute_command(char *command)
   {
    FILE *fpipe;
   char line[1024]="";
    //char *line = (char*)malloc(1024*sizeof(char));
   int i =0;

    if ( !(fpipe = (FILE*)popen(command,"r")) )
    {  // If fpipe is NULL
     perror("Problems with pipe");
     exit(1);
    }

     while ( fgets( line, sizeof line, fpipe))
    {
            //     printf("%s", line);
    }

    while(line[i]!='\0')
    {
    if(line[i]==' ')
    {
    line[i]=',';
    }
    i++;
    }
    pclose(fpipe);
    printf("%s",line);//This is where i want to know what the buffer has when the script returns nothing 
    return(line);

}

May be a simple one.. I got stuck in this.. help me.

Thanks in advance

Answer 1

According to this fgets man page, if end-of-file occurs before any characters are read, it returns NULL and the buffer contents remain unchanged.