[TypeSK]

please tell me this is a valid statement:

int main()
{
char *andfinder;

.
.
.

*andfinder = "Y";
*andfinder = "\0";
.
.
.
}

it wont compile ....

i got a pointer cycling through a string, and when it finds a certain character (in my case, "&"), i want it to be replaced with another character .....

as far as i know, using the * will dereference the pointer ... so you get whatever its pointing to

for ex:

char *ptr;

*ptr --> |A|

so if i use the following statement:

*ptr = "B";

then it should look like this

*ptr --> |B|

correct?

or am i missing something?

[TypeSK]

here is my code, as a reference to what im trying to do ....

here is the code for that ...

int main()
{

char incmd[MAX];
char *cmd[64];
char *cdcmd[64];
char *cddir[64];
char *andfinder;
int i, j, pid, status, ret_value, tmp;
int isBEx = 0;

      j = 0;

/* i is set to the # of words in the whole string
    j is just the current word it is on */

      while (j<i)
        {
          andfinder = cmd[j];
          while ((strcmp(andfinder, "\0")) == 1)
            {
              if (strcmp(andfinder, "&") == 0)
                {
                  printf("you found a AND sign\n");
                  isBEx = 1;
                  andfinder = "Y";
                  printf("%s\n", cmd[j]);
                }
              andfinder++;
            }
          j++;
        }

[TypeSK]

anyone?

[Shadow2531]

Is that all of it?

If not, we need all of it.

From what you posted, MAX is undefined and i, pid, status, ret_value, tmp are uninitialized.

incmd,cdcmd,cddir,pid,status,ret_value,tmp are not used.

What header files did you include
What errors did you get when you tried to compile it.

I await the rest of the code.

What compiler are you using?
Does this have to be in c or will c++ do?

Fill in the missing pieces and we'll go from there.

test.c

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

int main() {
    char incmd[MAX];
    char *cmd[64];
    char *cdcmd[64];
    char *cddir[64];
    char *andfinder;
    int i, j, pid, status, ret_value, tmp;
    int isBEx = 0;
    j = 0;
    while (j < i) {
        andfinder = cmd[j];
        while ((strcmp(andfinder, "\0")) == 1) {
            if (strcmp(andfinder, "&") == 0) {
                printf("you found a AND sign\n");
                isBEx = 1;
                andfinder = "Y";
                printf("%s\n", cmd[j]);
            }
              andfinder++;
        }
        j++;
    }
    exit(EXIT_SUCCESS);
}

[TypeSK]

sorry i didnt post the whole thing ... but i found the solution?

i did this:

old::

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

int main() {
    char incmd[MAX];
    char *cmd[64];
    char *cdcmd[64];
    char *cddir[64];
    char *andfinder;
    int i, j, pid, status, ret_value, tmp;
    int isBEx = 0;
    j = 0;
    while (j < i) {
        andfinder = cmd[j];
        while ((strcmp(andfinder, "\0")) == 1) {
            if (strcmp(andfinder, "&") == 0) {
                printf("you found a AND sign\n");
                isBEx = 1;
                andfinder = "Y";
                printf("%s\n", cmd[j]);
            }
              andfinder++;
        }
        j++;
    }
    exit(EXIT_SUCCESS);
}

new::

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

int main() {
    char incmd[MAX];
    char *cmd[64];
    char *cdcmd[64];
    char *cddir[64];
    char *andfinder;
    int i, j, pid, status, ret_value, tmp;
    int isBEx = 0;
    j = 0;
    while (j < i) {
        andfinder = cmd[j];
        while ((strcmp(andfinder, "\0")) == 1) {
            if (strcmp(andfinder, "&") == 0) {
                   printf("you found a AND sign\n");
                  isBEx = 1;
                  printf("%s\n", cmd[j]);
                }
              andfinder++;
            }
          j++;
        }

      if (isBEx == 1)
        {
          j = i;
          andfinder--;
          *andfinder = '\0';
        }

basically, i took it out of the loop and did it seperately? kinda weird ......

i did it in C ..compiling with gcc ...

error message was something about casting from int to char or something to that sort ....


here is my whole code, which works ... its just a basic minishell program... executes basic commands, and if needed, Ctl-C stops whatever your running (like an infinite loop) while not stopping the whole shell itself ..

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>

const int MAX = 1024;
int bgp;

void prntcmd ();
void ctlC_h(int sig);


int main()
{

  char incmd[MAX];
  char *cmd[64];
  char *cdcmd[64];
  char *cddir[64];
  char *andfinder;
  int i, j, pid, status, ret_value, tmp;
  int isBEx = 0; /* 0 = NO executes in background 1 = executes in background*/

  signal(SIGINT, ctlC_h);


  while (1)
    {

    prt_prompt:
      printf("sh%% ");
      fgets (incmd, MAX, stdin);

      if (strcmp(incmd, "\n") == 0)
        goto prt_prompt;

      i = 0;
      cmd[i] = strtok (incmd," \n\t");

      while (cmd[i] != NULL) {
        i++;
        cmd[i] = strtok(NULL," \n\t");
      }

      j = 0;

      while (j<i)
        {
          andfinder = cmd[j];
          while ((strcmp(andfinder, "\0")) == 1)
            {
              if (strcmp(andfinder, "&") == 0)
                {
                  isBEx = 1;
                }
              andfinder++;
            }
          j++;
        }

      if (isBEx == 1)
        {
          j = i;
          andfinder--;
          *andfinder = '\0';
        }

      if (strcmp(*cmd, "bye") == 0)
        break;

        if (strcmp(*cmd, "?") == 0)
          prntcmd();

        if (strcmp(*cmd, "cd") == 0)
          chdir(cmd[1]);

        isBEx = 0;

      pid=fork();
      if (pid==0)
        {
          if (strcmp(*cmd, "?") != 0 && strcmp(*cmd, "cd") != 0)
            execvp(*cmd, cmd);
          exit(0);
        }
      else if (pid>0)
        {
          if (isBEx == 0)
            ret_value=wait(&status);
        }

    }

  return 0;
}


void prntcmd ()
{
  printf(" ls                                 -- list files in current directory\n");
  printf(" cd <dir_name>                      -- change directory\n");
  printf(" emacs <file_name>                  -- opens emacs file editor\n");
  printf(" ps                                 -- lists current processes\n");
  printf(" mk <dir_name>                      -- creates a new directory\n");
  printf(" rm <file_name>                     -- deletes the filename\n");
  printf(" cp <old file_name> <new file_name> -- copies the file to a new file\n");
  printf(" ?                                  -- brings up this menu\n");
}

void ctlC_h(int sig)
{

}

[codejockey]

OK, let's start at the beginning ...

You need to distinguish between a character and a character string. When you dereference a pointer to a character, you get a character (NOT a character string). So, for example, if you have declared a pointer to a character such as:

char *charp = "This is a character string";

then *charp dereferences to 'T' -- i.e., one, single character (a capital 'T'). You may, if you choose, assign this character pointer to another string (e.g., charp = "Another string"); in this case, *charp now dereferences to 'A'. The compiler treats a single character as an int (integer) whose value is the ASCII value of the character (e.g., 0x41 is 'A'). An integer is not the same as a pointer, and most compilers will complain. When you use a quoted string, the compiler translates this into a pointer reference; a statement such as *charp = "Y" attempts to assign what charp points to (a character) to a pointer reference ("Y") which generally causes problems with most compilers (). More details available on request.

And no -- not stupid, not easy, and a source of confusion for lots of programmers.

Hope this helps.