pid_t exec_command(char *comm_name,char **args,int flags,pid_t group_id,int infile,int outfile){
pid_t cpid = fork();
int hist_ret;
if(cpid==0){
//child:
//Reset Signals
signal (SIGINT ,SIG_DFL);
signal (SIGQUIT,SIG_DFL);
signal (SIGTSTP,SIG_DFL);
signal (SIGTTIN,SIG_DFL);
signal (SIGTTOU,SIG_DFL);
signal (SIGCHLD,SIG_DFL);
cpid=getpid();
if(group_id==0)group_id=cpid;
setpgid(cpid,group_id);
if(infile!=STDIN_FILENO){
dup2(infile,STDIN_FILENO);
close(infile);
}
if(outfile!=STDOUT_FILENO){
dup2(outfile,STDOUT_FILENO);
close(outfile);
}
if(flags&EXEC_FLAG_BACKGROUND){
}
else{
tcsetpgrp(shell_in,group_id);
}
if(!strcmp(comm_name,"pid")){
exec_pid(args);
exit(0);
}
else if((hist_ret=check_hist_str(comm_name))!=-1){
//Check for hist command and process hist #TODz
exec_hist(hist_ret);
exit(0);
}
else{
int execret=execvp(comm_name,args);
if(execret==-1){
error(0,0,"%s : %s\n",comm_name,strerror(errno));
exit(2);
}
}
}
else{
//parent:
if(infile!=STDIN_FILENO)
close(infile);
if(outfile!=STDOUT_FILENO)
close(outfile);
process_list[plist_end].pid=cpid;
process_list[plist_end].process_name=strdup(args[0]);
plist_end=(plist_end+1)%PLIST_LENGTH_MAX;
if(plist_end==plist_start)plist_start=(plist_start+1)%PLIST_LENGTH_MAX;
if(group_id==0)group_id=cpid;
setpgid(cpid,group_id);
if(flags&(EXEC_FLAG_BACKGROUND)){
//add process to ActiveProcess list and continue
active_process_list[actv_plist_cnt].pid=cpid;
active_process_list[actv_plist_cnt].process_name=strdup(args[0]);
actv_plist_cnt++;
if(actv_plist_cnt>=PLIST_LENGTH_MAX){
error(0,0,"Cannot manage more than %d Active Processes. Process Killed\n",PLIST_LENGTH_MAX);
kill(cpid,SIGKILL);
actv_plist_cnt--;
}
}
else if(flags&(EXEC_MORE_PIPES)){
tcsetpgrp(shell_in,group_id);
}
else{
//wait patiently till process exits
tcsetpgrp(shell_in,group_id);
waitpid(cpid,NULL,0);
tcsetpgrp(shell_in,mypid);
}
}
return cpid;
}
// Invokes a command, assuming it has no pipes.
int invoke(char *input, int will_fork) {
int stdin_copy = dup(0);
int stdout_copy = dup(1);
// First, we want to determine whether we need any redirects.
char **files = tokenize_redirects(input);
unsigned int i;
char *infile = NULL;
char *outfile = NULL;
int status;
// Clean up the array contents.
char **tokens = tokenize(files[0]);
char **infiles;
if (files[1]) {
infiles = tokenize(files[1]);
infile = infiles[0];
}
char **outfiles;
if (files[2]) {
outfiles = tokenize(files[2]);
outfile = outfiles[0];
}
if (infile) {
int in_fd = open(infile, O_RDONLY);
if (in_fd == -1) {
fprintf(stderr, "open failed: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
dup2(in_fd, STDIN_FILENO);
status = close(in_fd);
if (status == -1) {
fprintf(stderr, "close failed: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
}
if (outfile) {
int out_fd = open(outfile, O_CREAT | O_TRUNC | O_WRONLY,
S_IRUSR | S_IWUSR);
if (out_fd == -1) {
fprintf(stderr, "open failed: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
dup2(out_fd, STDOUT_FILENO);
status = close(out_fd);
if (status == -1) {
fprintf(stderr, "close failed: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
}
// Handle built in commands.
if (!tokens[0]) return 0;
if (strcmp(tokens[0], "cd") == 0 || strcmp(tokens[0], "chdir") == 0) {
exec_cd(tokens);
}
else if (strcmp(tokens[0], "history") == 0) {
exec_hist(tokens);
}
else if (strcmp(tokens[0], "exit") == 0) {
exit(EXIT_SUCCESS);
}
else {
if (will_fork) { // Based on how invoke is called, fork.
pid_t pid = fork();
if (pid == -1) {
fprintf(stderr, "fork failed: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
else if (pid == 0) {
if (execvp(tokens[0], tokens) == -1) {
fprintf(stderr, "execvp failed: %s\n", strerror(errno));
}
}
else {
wait(&status);
}
}
else {
if (execvp(tokens[0], tokens) == -1) {
fprintf(stderr, "execvp failed: %s\n", strerror(errno));
}
}
}
dup2(stdin_copy, STDIN_FILENO);
dup2(stdout_copy, STDOUT_FILENO);
// Memory management.
for (i = 0; tokens[i] != NULL; i++) {
free(tokens[i]);
}
free(tokens);
if (files[1]) {
for (i = 0; infiles[i] != NULL; i++) {
free(infiles[i]);
}
free(infiles);
}
if (files[2]) {
for (i = 0; outfiles[i] != NULL; i++) {
free(outfiles[i]);
}
free(outfiles);
}
for (i = 0; i < 3; i++) {
if (files[i]) {
free(files[i]);
}
}
free(files);
return 0;
}
