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#include "cmd.h"
Command *newCmd() {
Command *cmd = (Command *)malloc(sizeof(Command));
cmd->argc = 0;
cmd->args = NULL;
cmd->type = CMD_NORMAL;
cmd->left = NULL;
cmd->right = NULL;
for (int i = 0; i < 3; i++) {
cmd->redirectFile[i] = NULL;
cmd->redirectFD[i] = i;
}
cmd->background = false;
return cmd;
}
void freeCmd(Command *cmd) {
if (cmd == NULL) {
return;
}
if (cmd->left != NULL) {
freeCmd(cmd->left);
}
if (cmd->right != NULL) {
freeCmd(cmd->right);
}
int i;
for (i = 0; i < cmd->argc; i++) {
free(cmd->args[i]);
}
free(cmd->args);
for (i = 0; i < 3; i++) {
if (cmd->redirectFile[i] != NULL) {
free(cmd->redirectFile[i]);
}
}
free(cmd);
}
int runCmd(Command *cmd) {
int status;
if (cmd == NULL) {
fprintf(stderr, "cmd is NULL\n");
return -1;
}
switch (cmd->type) {
case CMD_NORMAL:
status = runNormalCmd(cmd);
break;
case CMD_PIPE:
status = runPipeCmd(cmd);
break;
case CMD_AND:
case CMD_OR:
status = runAndOrCmd(cmd);
break;
}
freeCmd(cmd);
return status;
}
int runNormalCmd(Command *cmd) {
pid_t pid;
int status;
if (!strcmp(cmd->args[0], "exit")) {
printf("Good Bye, %s!\n", username);
exit(0);
} else if (!strcmp(cmd->args[0], "cd")) {
if (cmd->argc == 1) {
chdir(getenv("HOME"));
} else {
chdir(cmd->args[1]);
}
printf("\r");
getcwd(pwd, sizeof(pwd));
} else {
if ((pid = fork()) == 0) {
// consider the redirection now
// it's just a part of normal command
// but not in other commands
redirect(cmd);
exit(execvp(cmd->args[0], cmd->args));
} else {
if (!cmd->background) {
waitpid(pid, &status, 0);
if (!WIFEXITED(status)) {
if (WIFSIGNALED(status)) {
fprintf(stderr, "Process %d was killed by signal %d\n",
pid, WTERMSIG(status));
} else {
fprintf(stderr, "Process %d exited with status %d\n",
pid, WEXITSTATUS(status));
}
}
}
}
// return the exit status of the child process
return WEXITSTATUS(status);
}
}
int runPipeCmd(Command *cmd) {
int status;
// create a pipe file and gets two file descriptors
// fd[0] is the read end, while fd[1] the write end
int fd[2];
pid_t left, right;
pipe(fd);
if ((left = fork()) == 0) {
/*
* close the read end of the pipe, so that the child process
* can only write to it; then redirect the standard output
* to the write end of the pipe, and close the write end
* itself as a file descriptor.
*/
close(fd[0]);
dup2(fd[1], 1);
close(fd[1]);
exit(runCmd(cmd->left));
}
if ((right = fork()) == 0) {
close(fd[1]);
dup2(fd[0], 0);
close(fd[0]);
exit(runCmd(cmd->right));
}
// close the pipe, because the parent process doesn't need it
// and wait for the two child processes to exit
close(fd[0]);
close(fd[1]);
waitpid(left, NULL, 0);
waitpid(right, NULL, 0);
}
int runAndOrCmd(Command *cmd) {
int status;
if (cmd->type == CMD_AND) {
if (fork() == 0) {
exit(runCmd(cmd->left));
} else {
waitpid(-1, &status, 0);
if (WIFEXITED(status) && WEXITSTATUS(status) == 0 && fork() == 0) {
status = runCmd(cmd->right);
}
wait(NULL);
}
} else if (cmd->type == CMD_OR) {
if (fork() == 0) {
exit(runCmd(cmd->left));
} else {
waitpid(-1, &status, 0);
if (WIFEXITED(status) && WEXITSTATUS(status) != 0 && fork() == 0) {
status = runCmd(cmd->right);
}
wait(NULL);
}
}
}
void redirect(Command *cur) {
int fd;
char *rfile;
for (int i = 0; i < 3; i++) {
fd = cur->redirectFD[i];
rfile = cur->redirectFile[i];
if (fd < -1 || fd > 2) {
fprintf(stderr, "file descriptor %d is invalid\n", fd);
exit(1);
}
if (fd == i && rfile == NULL) {
continue;
}
if (fd == -1) {
// append
fd = open(rfile, O_WRONLY | O_CREAT | O_APPEND, 0666);
} else if (rfile != NULL) {
// normal redirection
fd = open(rfile, O_WRONLY | O_CREAT | O_TRUNC, 0666);
} else {
// file descriptor redirection
// when here, fd is surely in 0, 1, 2
;
}
if (fd < 0) {
fprintf(stderr, "open file %s failed\n", rfile);
exit(1);
}
close(i);
dup2(fd, i);
close(fd);
}
}
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