concatenating strings to use on the command line-CodePudding

My assignment wants me to gather all the processes being run by using a ps -ef | grep -v grep | grep <PID#> I need to use, but I am receiving an illegal hardware instruction. here is the code:

//some code^

int PID = getpid();
char command[] = "ps -ef | grep -v grep | grep ";
char PIDString[12];

sprintf(PIDString, "%i", PID);
system("clear");

//These print just fine
//printf("%s\n",command);
//printf("ID %s",PIDString);

strcat(command, PIDString);

system(command);

When I tried to insert a %i. into the string "grep ...%.." it wouldn't work. Is there a way to do this instead of changing the int to a string and concatenating them. Please let me know what I'm missing to grasp.

CodePudding user response：

char command[] = "ps -ef | grep -v grep | grep ";

Your compiler will allocate just enough memory to hold this string.

If you want to have additional space available, you could make sure by specifying the size of the array.

char command[100] = "ps -ef | grep -v grep | grep ";

You may wish to define a constant to hold that value, rather than just a magic number.