Hi, i have to make my own unix shell (Which works like csh, tcsh and so on), i've created a basic shell and it works (i will post it below), but there are a very problems which i cannot figure out.

1)How do i make the shell exit when the user types (exit or control-D)
(something tells me i have to use a signal handler...but the various one's i've tried did not work...Grrrr)

second problem (this one is worse than the first)

If a child process is running @ foreground, the user can send the interrupt singal (Control-C) to terminate the child process, but the current parent process should not die.

Thanks []v[]atty-D

-------------------------------------------------------------
#include <stdio.h>
#include <string.h>
#include <unistd.h>
pid_t myFork();
int readArgs(const char *, char *[]);
int main(int argc, char *argv[]){
pid_t pid;
char line[255];
char *argList[20];
int ampersand, status, i;
printf("This program executes commands and\n");
printf("programs for you\n");
while(1){
printf("To exit, enter CTR-C, or enter\n");
printf("a program name with its arguments> ");
fgets(line, 255, stdin);
ampersand=readArgs(line, argList);
if((pid = myFork()) == -1){
perror("impossible to fork");
exit(1);
}

if(pid > 0) // This is the parent
if(ampersand) // Background execution
printf("Process [%d]\n", pid);
else{
waitpid(pid, &status, 0);
printf("My child has terminated\n");
}
else // this is the child
if(execvp(argList[0], argList)==-1){
perror("child Process");
exit(22);
}
}
}

pid_t myFork(){
static int count=0;
count++;
if(count <= 20)
return(fork());
else
return(-1);
}

int readArgs(const char *line, char *argList[]){
static int yes=0;
int i=0, offset=0, found=0;
char name[50];
while(yes && argList[i] != NULL)
free(argList[i++]);
i=0; // reset i to ZERO
while(sscanf(line+offset, "%s", name)==1){
argList[i] = (char *) malloc(strlen(name)+1);
strcpy(argList[i++], name);
while(line[offset]==' ') offset++; //skip blanks
offset += strlen(name);
}

if(!strcmp(argList[i-1], "&")){
argList[i-1] = NULL;
found = 1;
}
else{
if(argList[i-1][strlen(argList[i-1])-1]=='&'){
argList[i-1][strlen(argList[i-1])-1]='\0';
found = 1;
}
argList[i] = NULL;
}
yes=1;
return(found);
}

: Hi, i have to make my own unix shell (Which works like csh, tcsh and so on), i've created a basic shell and it works (i will post it below), but there are a very problems which i cannot figure out.
:
: 1)How do i make the shell exit when the user types (exit or control-D)
: (something tells me i have to use a signal handler...but the various one's i've tried did not work...Grrrr)
:
: second problem (this one is worse than the first)
:
: If a child process is running @ foreground, the user can send the interrupt singal (Control-C) to terminate the child process, but the current parent process should not die.
:
: Thanks []v[]atty-D
:
Now we can read it.
: -------------------------------------------------------------

: #include <stdio.h>
: #include <string.h>
: #include <unistd.h>
: pid_t myFork();
: int readArgs(const char *, char *[]);
: int main(int argc, char *argv[]){
: pid_t pid;
: char line[255];
: char *argList[20];
: int ampersand, status, i;
:    printf("This program executes commands and\n");
:    printf("programs for you\n");
:      while(1){
:       printf("To exit, enter CTR-C, or enter\n");
:       printf("a program name with its arguments> ");
:       fgets(line, 255, stdin);
:       ampersand=readArgs(line, argList);
:       if((pid = myFork()) == -1){
:            perror("impossible to fork");
:            exit(1);
:          }
: 
:       if(pid > 0) // This is the parent
:           if(ampersand) // Background execution
:                printf("Process [%d]\n", pid);
:            else{
:                  waitpid(pid, &status, 0);
:                  printf("My child has terminated\n");
:                 }
:      else // this is the child
:         if(execvp(argList[0], argList)==-1){
:         perror("child Process");
:         exit(22);
:       }
:     }
:   }
: 
: pid_t myFork(){
:   static int count=0;
:   count++;
:   if(count <= 20)
:   return(fork());
:   else
:   return(-1);
: }
: 
: int readArgs(const char *line, char *argList[]){
: static int yes=0;
: int i=0, offset=0, found=0;
: char name[50];
: while(yes && argList[i] != NULL)
: free(argList[i++]);
: i=0; // reset i to ZERO
: while(sscanf(line+offset, "%s", name)==1){
: argList[i] = (char *) malloc(strlen(name)+1);
: strcpy(argList[i++], name);
: while(line[offset]==' ') offset++; //skip blanks
: offset += strlen(name);
: }
: 
: if(!strcmp(argList[i-1], "&")){
: argList[i-1] = NULL;
: found = 1;
: }
: else{
: if(argList[i-1][strlen(argList[i-1])-1]=='&'){
: argList[i-1][strlen(argList[i-1])-1]='\0';
: found = 1;
: }
: argList[i] = NULL;
: }
: yes=1;
: return(found);
: }
: 

Ok i think i sorta figured out Part 2, but part 1 is still giving me problems. Someone told me instead of using a alarm handler i have to edit the string, whatever that means lol.

: Ok i think i sorta figured out Part 2, but part 1 is still giving me problems. Someone told me instead of using a alarm handler i have to edit the string, whatever that means lol.
:

actually, part 2 is rather easy. when doing Ctrl-C, the controlling terminal sends SIGINT to the foreground process group. all you have to do is ignore it in the parent while there's a child running.

...
if(pid > 0)
{
...
    signal(SIGINT, SIG_IGN);
    waitpid(pid, &status, 0);
    signal(SIGTSTP, SIG_DFL);
...
}

for part 1, you need to figure out what was entered, so parse the input. to break it down into pieces:

...
fgets(line, 255, stdin);
if(10 == line[0]) /*ENTER or Ctrl-D will give you this*/
    exit(0);
if('e' == line[0] && !strncmp(line, "exit",4) )
    exit(0);
/*otherwise proceed with interpreting the command*/
...