// Executes an <and-or> rooted with cmd and returns the status of the last
// command executed.
int processAndOr(CMD* cmd)
{
assert(cmd);
assert(cmd->type != SEP_BG && cmd->type != SEP_END);
int lastStatus = 0; // status of last command executed
if(cmd->type == SEP_AND)
{
if((lastStatus = processPipeline(cmd->left)) == 0)
{
lastStatus = processAndOr(cmd->right);
}
}
else if(cmd->type == SEP_OR)
{
if((lastStatus = processPipeline(cmd->left)) != 0)
{
lastStatus = processAndOr(cmd->right);
}
}
else
{
lastStatus = processPipeline(cmd);
}
return lastStatus;
}
/*
use: process an <and-or>
args:
cmd = root of command tree
status = status of process
skip = greedy flag
return: status of process
*/
int processAndOr(CMD* cmd, int status, bool skip) {
// <pipeline> && <and-or> case
if (cmd->type == SEP_AND) {
// left child
if (!skip) {
status = processPipe(cmd->left, 0, false);
}
// if left child is true, do right
if (status == 0) {
status = processAndOr(cmd->right, status, false);
}
else {
status = processAndOr(cmd->right, status, true);
}
}
// <pipeline> || <and-or> case
else if (cmd->type == SEP_OR) {
// left child
if (!skip) {
status = processPipe(cmd->left, 0, false);
}
// if left child is false, do right
if (status != 0) {
status = processAndOr(cmd->right, status, false);
}
else {
status = processAndOr(cmd->right, status, true);
}
}
// <pipeline> case
else {
if (!skip) {
status = processPipe(cmd, 0, false);
}
}
return status;
}
int process(CMD* cmd)
{
if(!cmd) return 0;
int zombieStatus; // never used after passing to waitpid
while(waitpid(-1, &zombieStatus, WNOHANG) > 0); // reap zombie processes
int exitStatus;
if(cmd->type == SEP_BG)
{
if(cmd->left->type == SIMPLE)
{
processSimple(cmd->left, true);
}
else
{
processSubcommand(cmd->left, NULL, true);
}
exitStatus = process(cmd->right); // cmd->right may be NULL
}
else if(cmd->type == SEP_END)
{
if(!cmd->right)
{
exitStatus = processAndOr(cmd->left);
}
else
{
processAndOr(cmd->left);
exitStatus = process(cmd->right);
}
}
else
{
exitStatus = processAndOr(cmd);
}
return exitStatus;
}
/*
use: process a <command> or <list>
args: cmd = root of command tree
return: status of process
*/
int processCMD(CMD* cmd) {
int status; // status of process
// <and-or> ; <command> and <list> ; cases
if (cmd->type == SEP_END) {
// left child
status = processCMD(cmd->left);
// right child
if (cmd->right) {
status = processCMD(cmd->right);
}
}
// <and-or> & <command> and <list> & cases
else if (cmd->type == SEP_BG) {
pid_t pID = fork(); // process ID of fork
// error check
if (pID < 0) {
status = errno;
errorExit(status);
}
// child process
else if (pID == 0) {
status = processCMD(cmd->left);
exit(status);
}
// parent process
else {
status = 0;
fprintf(stderr, "Backgrounded: %d\n", pID);
if (cmd->right) {
status = processCMD(cmd->right);
}
}
}
// <and-or> case
else {
status = processAndOr(cmd, 0, false);
}
return status;
}
