/*BEGIN externalCall function--passes user input to external shell. Used only if user inputs a command not implemented in this shell*/
int externalCall(char **args){
/*check for the background execution argument '&'*/
BGCheck(args);
/*fork/exec statement--case 0 is the child process, default is the parent, -1 is an error*/
switch(childPID = fork()){
case -1:
debug("Fork error");
break;
case 0:
debug("Externalcall fork case 0");
/*allocate memory for, build, and push PARENT environment variable (used a previously made char* to save space*/
shell = (char*)malloc(sizeof(char) *(strlen(initCall) + 8));
strcat(shell, "PARENT=");
strcat(shell, initCall);
putenv(shell);
/*check for I/O Redirect, both in and out(all other calls currently used only check for output redirection)*/
IORedirect(args, 2);
execvp(args[0], args);
exit(-1); //exit with error code, shouldn't ever reach this line
default:
if(!noWait){
debug("Externalcall wait");
waitpid(childPID, &status, WUNTRACED);
}
}
return childPID;
}
//#iii. dir <directory> - list the contents of <directory>
int dir(char **args){
int i = 2;
numArgs = 0;
debug("Dir called");
/*count the arguments*/
while(args[++numArgs] != NULL);
/*allocate space for, and build the new set of arguments*/
out = (char**)malloc(sizeof(char*) * (numArgs + 1));
out[0] = (char *)malloc(sizeof(char) * 3);
strcpy(out[0], "ls");
out[1] = (char *)malloc(sizeof(char) * 4);
strcpy(out[1], "-al");
out[2] = NULL; //in case of no additional arguments
debug("Setting Args. List to follow:");
debug(out[0]);
debug(out[1]);
/*set the new list of arguments, terminated with a NULL pointer*/
while(i < numArgs+1){
out[i] = (char *)malloc(sizeof(char) * ((strlen(args[i-1]))+1));
strcpy(out[i], args[i-1]);
debug(out[i]);
++i;
out[i] = NULL;
}
/*fork/exec statement--case 0 is the child process, default is the parent, -1 is an error*/
switch(childPID = fork()){
case -1:
debug("Fork error");
break;
case 0:
debug("Dir fork case 0");
debug("Checking for I/O Redirection");
IORedirect(out, 1);
debug("I/O Redirection check complete. Executing call.");
execvp("ls", out);
exit(-1);
default:
if(!noWait){
debug("Dir wait");
waitpid(childPID, &status, WUNTRACED);
}
}
free(out);
return childPID;
}
/*
* eval - Evaluate the command line that the user has just typed in
*
* If the user has requested a built-in command (quit, jobs, bg or fg)
* then execute it immediately. Otherwise, fork a child process and
* run the job in the context of the child. If the job is running in
* the foreground, wait for it to terminate and then return. Note:
* each child process must have a unique process group ID so that our
* background children don't receive SIGINT (SIGTSTP) from the kernel
* when we type ctrl-c (ctrl-z) at the keyboard.
*/
void eval(char *cmdline)
{
int bg; /* should the job run in bg or fg? */
struct cmdline_tokens tok;
struct job_t *jobinfo;
pid_t pid;
sigset_t wait;
/* Parse command line */
bg = parseline(cmdline, &tok);
if (bg == -1) /* parsing error */
return;
if (tok.argv[0] == NULL) /* ignore empty lines */
return;
if(!buildinCmd(&tok)){
blockAllSignal();
if((pid = fork()) == 0){
//child
if(setpgid(0, 0) < 0){
unix_error("process set prcess group error\n");
}
IORedirect(&tok);
unblockAllSignal();
if(execve(tok.argv[0], tok.argv, environ) == -1){
printf("%s, command not found\n", tok.argv[0]);
exit(0);
}
}else{
//parent
if(!bg){
addjob(job_list, pid, FG, cmdline);
sigemptyset(&wait);
sigsuspend(&wait);
unblockAllSignal();
while(fgpid(job_list) != 0)
{
sigsuspend(&wait);
}
}else{
addjob(job_list, pid, BG, cmdline);
jobinfo = getjobpid(job_list, pid);
printf("[%d] (%d) %s\n", jobinfo->jid, jobinfo->pid, jobinfo->cmdline);
unblockAllSignal();
}
}
}
return;
}
//#vi. help - display the user manual using the more filter
int help(char **args){
debug("Help called");
/*fork/exec statement--case 0 is the child process, default is the parent, -1 is an error*/
switch(childPID = fork()){
case -1:
debug("Fork error");
break;
case 0:
IORedirect(args, 1);
/*Display the readme file using the more filter*/
execlp("more", "more", readme, NULL);
exit(-1);
default:
if(!noWait)
waitpid(childPID, &status, WUNTRACED);
}
return childPID;
}
//#iv. environ - list all the environment strings
int envrn(char **args){
debug("Environ called");
env = environ;
/*fork/exec statement--case 0 is the child process, default is the parent, -1 is an error*/
switch(childPID = fork()){
case -1:
debug("Fork Error");
break;
case 0:
IORedirect(args, 1);
while(*env)
puts(*env++);
exit(0);
default:
if(!noWait)
waitpid(childPID, &status, WUNTRACED);
}
return childPID;
}
//#v. echo <comment> - display <comment> on the display followed by
//#a new line (multiple spaces/tabs may be reduced to a single space)
int echo(char **args){
int i = 1;
debug("Echo called");
/*fork/exec statement--case 0 is the child process, default is the parent, -1 is an error*/
switch(childPID = fork()){
case -1:
debug("Fork error");
break;
case 0:
IORedirect(args, 1);
/*print all arguments on a single line, each followed by a single space.*/
while(args[i] != NULL){
printf("%s ", args[i]);
++i;
}
printf("\n"); //end the line with a newline character
exit(0);
default:
if(!noWait)
waitpid(childPID, &status, WUNTRACED);
}
return childPID;
}
