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tsh.c
1210 lines (1083 loc) · 26.7 KB
/
tsh.c
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/*
* COMP 321 Project 4: Shell
*
* This program implements a tiny shell with job control.
*
* Yejin Kim yk26
* Yue Zhang yz53
*/
#include <sys/types.h>
#include <sys/wait.h>
#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
// You may assume that these constants are large enough.
#define MAXLINE 1024 // max line size
#define MAXARGS 128 // max args on a command line
#define MAXJOBS 16 // max jobs at any point in time
#define MAXJID (1 << 16) // max job ID
// The job states are:
#define UNDEF 0 // undefined
#define FG 1 // running in foreground
#define BG 2 // running iyn background
#define ST 3 // stopped
/*
* The job state transitions and enabling actions are:
* FG -> ST : ctrl-z
* ST -> FG : fg command
* ST -> BG : bg command
* BG -> FG : fg command
* At most one job can be in the FG state.
*/
struct Job {
pid_t pid; // job PID
int jid; // job ID [1, 2, ...]
int state; // UNDEF, FG, BG, or ST
char cmdline[MAXLINE]; // command line
};
typedef volatile struct Job *JobP;
/*
* Define the jobs list using the "volatile" qualifier because it is accessed
* by a signal handler (as well as the main program).
*/
static volatile struct Job jobs[MAXJOBS];
static int nextjid = 1; // next job ID to allocate
extern char **environ; // defined by libc
static char prompt[] = "tsh> "; // command line prompt (DO NOT CHANGE)
static bool verbose = false; // If true, print additional output.
static char **directories; // store directories
static int directoryCount = 0;
/*
* The following array can be used to map a signal number to its name.
* This mapping is valid for x86(-64)/Linux systems, such as CLEAR.
* The mapping for other versions of Unix, such as FreeBSD, Mac OS X, or
* Solaris, differ!
*/
static const char *const signame[NSIG] = {
"Signal 0",
"HUP", /* SIGHUP */
"INT", /* SIGINT */
"QUIT", /* SIGQUIT */
"ILL", /* SIGILL */
"TRAP", /* SIGTRAP */
"ABRT", /* SIGABRT */
"BUS", /* SIGBUS */
"FPE", /* SIGFPE */
"KILL", /* SIGKILL */
"USR1", /* SIGUSR1 */
"SEGV", /* SIGSEGV */
"USR2", /* SIGUSR2 */
"PIPE", /* SIGPIPE */
"ALRM", /* SIGALRM */
"TERM", /* SIGTERM */
"STKFLT", /* SIGSTKFLT */
"CHLD", /* SIGCHLD */
"CONT", /* SIGCONT */
"STOP", /* SIGSTOP */
"TSTP", /* SIGTSTP */
"TTIN", /* SIGTTIN */
"TTOU", /* SIGTTOU */
"URG", /* SIGURG */
"XCPU", /* SIGXCPU */
"XFSZ", /* SIGXFSZ */
"VTALRM", /* SIGVTALRM */
"PROF", /* SIGPROF */
"WINCH", /* SIGWINCH */
"IO", /* SIGIO */
"PWR", /* SIGPWR */
"Signal 31"
};
// You must implement the following functions:
static void eval(const char *cmdline);
static int builtin_cmd(char **argv);
static void do_bgfg(char **argv);
static void waitfg(pid_t pid);
static void initpath(const char *pathstr);
static void sigchld_handler(int signum);
static void sigint_handler(int signum);
static void sigtstp_handler(int signum);
// We are providing the following functions to you:
static int parseline(const char *cmdline, char **argv);
static void sigquit_handler(int signum);
static void clearjob(JobP job);
static void initjobs(JobP jobs);
static int maxjid(JobP jobs);
static int addjob(JobP jobs, pid_t pid, int state, const char *cmdline);
static int deletejob(JobP jobs, pid_t pid);
static pid_t fgpid(JobP jobs);
static JobP getjobpid(JobP jobs, pid_t pid);
static JobP getjobjid(JobP jobs, int jid);
static int pid2jid(pid_t pid);
static void listjobs(JobP jobs);
static void usage(void);
static void unix_error(const char *msg);
static void app_error(const char *msg);
typedef void handler_t(int);
static handler_t *Signal(int signum, handler_t *handler);
static void Sio_error(char s[]);
static void sio_error(char s[]);
static void sio_ltoa(long v, char s[], int b);
static ssize_t Sio_putl(long v);
static ssize_t sio_putl(long v);
static ssize_t Sio_puts(char s[]);
static ssize_t sio_puts(char s[]);
static void sio_reverse(char s[]);
static size_t sio_strlen(char s[]);
/*
* main - The shell's main routine
*
* Requires:
* argc should be less than MAXARGS arguments.
* argv should contain less than MAXARGS arguments.
*
* Effects:
* Runs an interactive command-line interpreter that runs programs on
* behalf of the user. It waits for a command line and then carries out
* the action of that command line. The shell executes built-in commands
* immediately, but also can execute user programs by forking child
* processes. It manages jobs running the foreground and background.
*/
int
main(int argc, char **argv)
{
int c;
char cmdline[MAXLINE];
char *path = NULL;
bool emit_prompt = true; // Emit a prompt by default.
/*
* Redirect stderr to stdout (so that driver will get all output
* on the pipe connected to stdout).
*/
dup2(1, 2);
// Parse the command line.
while ((c = getopt(argc, argv, "hvp")) != -1) {
switch (c) {
case 'h': // Print a help message.
usage();
break;
case 'v': // Emit additional diagnostic info.
verbose = true;
break;
case 'p': // Don't print a prompt.
// This is handy for automatic testing.
emit_prompt = false;
break;
default:
usage();
}
}
// Install the signal handlers.
// These are the ones you will need to implement:
Signal(SIGINT, sigint_handler); // ctrl-c
Signal(SIGTSTP, sigtstp_handler); // ctrl-z
Signal(SIGCHLD, sigchld_handler); // Terminated or stopped child
// This one provides a clean way to kill the shell.
Signal(SIGQUIT, sigquit_handler);
// Initialize the search path.
path = getenv("PATH");
initpath(path);
// Initialize the jobs list.
initjobs(jobs);
// Execute the shell's read/eval loop.
while (true) {
// Read the command line.
if (emit_prompt) {
printf("%s", prompt);
fflush(stdout);
}
if ((fgets(cmdline, MAXLINE, stdin) == NULL) && ferror(stdin)){
app_error("fgets error");}
if (feof(stdin)) { // End of file (ctrl-d)
fflush(stdout);
exit(0);
}
// Evaluate the command line.
eval(cmdline);
fflush(stdout);
fflush(stdout);
}
// Control never reaches here.
assert(false);
}
/*
* 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.
*
* Requires:
* "cmdline" is a NUL ('\0') terminated string with a trailing
* '\n' character. "cmdline" must contain less than MAXARGS
* arguments.
*
* Effects:
* A built-in command is executed immediately. Otherwise, it attempts
* to fork a child process and execute the job. If necessary, the
* executable program is searched through the directories of the
* search path. If not found, an error is thrown. If the job is
* running as a foreground job, it waits until completion.
*/
static void
eval(const char *cmdline)
{
char *argv[MAXARGS];
int bg = parseline(cmdline, argv);
pid_t pid;
sigset_t mask;
// Checks command line is not empty.
if (!argv[0]) {
return;
}
// Checks that the command is not a built-in command.
if(!builtin_cmd(argv)){
sigemptyset(&mask);
sigaddset(&mask, SIGCHLD);
sigprocmask(SIG_BLOCK, &mask, NULL);
// A child is forked.
pid = fork();
if (pid == 0) {
// Put child in new group whose ID is identical to child’s PID.
setpgid(0, 0);
sigprocmask(SIG_UNBLOCK, &mask, NULL);
if (execve(argv[0], argv, environ) == -1) {
int index = 0;
// Run through directories in search path to execute program.
while (argv[0][0] != '.' && index < directoryCount) {
if (execve(strcat(directories[index],argv[0]), argv, environ) != -1) {
break;
}
index++;
}
// Command not found.
char *print;
asprintf(&print, "%s: Command not found\n", argv[0]);
sio_error(print);
}
}
if (bg == 0) {
addjob(jobs,pid,FG,cmdline);
sigprocmask(SIG_UNBLOCK, &mask, NULL);
// Wait for foreground jobs to complete.
waitfg(pid);
}
else {
addjob(jobs,pid,BG,cmdline);
sigprocmask(SIG_UNBLOCK, &mask, NULL);
printf("[%d] (%d) %s", pid2jid(pid), pid, cmdline);
}
}
return;
}
/*
* parseline - Parse the command line and build the argv array.
*
* Requires:
* "cmdline" is a NUL ('\0') terminated string with a trailing
* '\n' character. "cmdline" must contain less than MAXARGS
* arguments.
*
* Effects:
* Builds "argv" array from space delimited arguments on the command line.
* The final element of "argv" is set to NULL. Characters enclosed in
* single quotes are treated as a single argument. Returns true if
* the user has requested a BG job and false if the user has requested
* a FG job.
*/
static int
parseline(const char *cmdline, char **argv)
{
int argc; // number of args
int bg; // background job?
static char array[MAXLINE]; // local copy of command line
char *buf = array; // ptr that traverses command line
char *delim; // points to first space delimiter
strcpy(buf, cmdline);
// Replace trailing '\n' with space.
buf[strlen(buf) - 1] = ' ';
// Ignore leading spaces.
while (*buf != '\0' && *buf == ' ')
buf++;
// Build the argv list.
argc = 0;
if (*buf == '\'') {
buf++;
delim = strchr(buf, '\'');
} else
delim = strchr(buf, ' ');
while (delim != NULL) {
argv[argc++] = buf;
*delim = '\0';
buf = delim + 1;
while (*buf != '\0' && *buf == ' ') // Ignore spaces.
buf++;
if (*buf == '\'') {
buf++;
delim = strchr(buf, '\'');
} else
delim = strchr(buf, ' ');
}
argv[argc] = NULL;
// Ignore blank line.
if (argc == 0)
return (1);
// Should the job run in the background?
if ((bg = (*argv[argc - 1] == '&')) != 0)
argv[--argc] = NULL;
return (bg);
}
/*
* builtin_cmd - If the user has typed a built-in command then execute
* it immediately.
*
* Requires:
* argv should contain less than MAXARGS arguments.
*
* Effects:
* Checks the type of command and calls the appropriate function.
* If the command is not a built-in command, the function returns 0.
*/
static int
builtin_cmd(char **argv)
{
if (strcmp("quit", argv[0]) == 0) {
exit(0);
}
else if (strcmp("jobs", argv[0]) == 0) {
listjobs(jobs);
return 1;
}
else if (strcmp("bg", argv[0]) == 0) {
do_bgfg(argv);
return 1;
}
else if (strcmp("fg", argv[0]) == 0) {
do_bgfg(argv);
return 1;
}
// This is not a build-in command.
return 0;
}
/*
* do_bgfg - Execute the built-in bg and fg commands.
*
* Requires:
* argv should contain less than MAXARGS arguments.
*
* Effects:
* Checks the validity of the arguments and changes
* the states of the jobs to either foreground or background.
*/
static void
do_bgfg(char **argv)
{
JobP currJob;
if (argv[1] == NULL) {
return;
}
// Check if argument is PID.
if (isdigit(argv[1][0])) {
// There is no such pid job.
if ((currJob = getjobpid(jobs, atoi(argv[1]))) == NULL) {
return;
}
}
// Check if argument is JID.
else if (argv[1][0] == '%') {
// There is no such jid job.
if ((currJob = getjobjid(jobs, atoi(&argv[1][1]))) == NULL) {
return;
}
}
else {
return;
}
// Send out SIGCONT to processes in process group of currJob
if (currJob->state == ST) {
kill(-currJob->pid, SIGCONT);
}
if (strcmp("fg", argv[0]) == 0) {
currJob->state = FG;
// Wait for foreground jobs to complete.
waitfg(currJob->pid);
}
else if (strcmp("bg", argv[0]) == 0) {
currJob->state = BG;
printf("[%d] (%d) %s", currJob->jid, currJob->pid, currJob->cmdline);
}
else {
return;
}
}
/*
* waitfg - Block until process pid is no longer the foreground process.
*
* Requires:
* Non-null pid.
*
* Effects:
* Waits for a foreground job to complete.
*/
static void
waitfg(pid_t pid)
{
sigset_t mask;
if (sigemptyset(&mask) < 0)
perror("sigemptyset");
while (1) {
// If the foreground job completes, return
if (fgpid(jobs) != pid) {
return;
}
// Else suspend/block
sigsuspend(&mask);
}
return;
}
/*
* addDirectory - Helper function to add directory to directories array
*
* Requires:
* Length of directories array is not exceeded
*
* Effects:
* Add directory to directories array
*/
static void
addDirectory(char *directory) {
directories[directoryCount] = directory;
directoryCount++;
}
/*
* initpath - Perform all necessary initialization of the search path,
* which may be simply saving the path.
*
* Requires:
* "pathstr" is a valid search path.
*
* Effects:
* Initialize search path.
*/
static void
initpath(const char *pathstr)
{
// Find out how many directories are in PATH.
size_t count = 1;
char *pathstr_copy = pathstr;
while(*pathstr_copy != '\0') {
count += *pathstr_copy++ == ':';
}
directories = malloc(sizeof(char **) * count);
int curr_index = 0;
int starting_index = 0;
bool colon = false;
// Parse search path into directories using colon as delimiter.
while (true) {
char c= pathstr[curr_index];
if (c == '\0') {
// If path ends with colon or path is empty, interpret as current directory.
if (colon || curr_index == 0) {
addDirectory("");
}
else {
int size = curr_index - starting_index;
char *currDirectory = malloc(sizeof(char*) * size);
strncpy(currDirectory, &pathstr[starting_index], size);
addDirectory(currDirectory);
}
break;
}
if (c == ':') {
/* If two colons in a row or path starts with colon,
interpret as current directory. */
if (colon || curr_index == 0) {
addDirectory("");
}
else {
colon = true;
int size = curr_index - starting_index;
char *currDirectory = malloc(sizeof(char*) * size);
strncpy(currDirectory, &pathstr[starting_index], size);
addDirectory(currDirectory);
starting_index = curr_index + 1;
}
}
else colon = false;
curr_index++;
}
}
/*
* The signal handlers follow.
*/
/*
* sigchld_handler - The kernel sends a SIGCHLD to the shell whenever
* a child job terminates (becomes a zombie), or stops because it
* received a SIGSTOP or SIGTSTP signal. The handler reaps all
* available zombie children, but doesn't wait for any other
* currently running children to terminate.
*
* Requires:
* When a child job terminates or stops, it sends out signal successfully
*
* Effects:
* If the child job is stopped by a signal, change its state and print signal
* information; if the child job is terminated by a signal, print signal
* information and delete the child job; if the child job is terminated in
* other ways, delete it. The handler reaps all available zombie children,
* but doesn't wait for any currently running children to terminate.
*/
static void
sigchld_handler(int signum)
{
// Prevent an "unused parameter" warning.
(void)signum;
pid_t pid;
int status;
// Reap zombie children but doesn't wait for currently running children
while ((pid = waitpid(-1, &status, WNOHANG | WUNTRACED)) > 0) {
struct Job *pcurjob = getjobpid(jobs, pid);
if (!pcurjob) {
app_error("pcurjob in sigtstp_handler");
}
// If a child stops, change its state to ST and print the information
if (WIFSTOPPED(status)) {
pcurjob->state = ST;
char *print;
asprintf(&print, "Job [%d] (%d) stopped by signal SIGTSTP\n", pid2jid(pid), pid);
sio_puts(print);
}
// If a child terminates by signal, print the information and delete the job
else if (WIFSIGNALED(status)) {
char *print;
asprintf(&print, "Job [%d] (%d) terminated by signal SIGINT\n", pcurjob->jid, pcurjob->pid);
sio_puts(print);
deletejob(jobs, pid);
}
// Delete the job is the child terminates in any other way
else {
deletejob(jobs, pid);
}
}
return;
}
/*
* sigint_handler - The kernel sends a SIGINT to the shell whenever the
* user types ctrl-c at the keyboard. Catch it and send it along
* to the foreground job.
*
* Requires:
* SIGINT is sent out successfully
*
* Effects:
* Send SIGINT to every process in the process group of current foreground job
*/
static void
sigint_handler(int signum)
{
// Prevent an "unused parameter" warning.
(void)signum;
pid_t pid;
// Get pid of current foreground job
if ((pid = fgpid(jobs)) <= 0) {
return;
}
// Send SIGINT to every process in process group |pid|
if (kill(-pid, SIGINT) < 0) {
perror("kill");
}
return;
}
/*
* sigtstp_handler - The kernel sends a SIGTSTP to the shell whenever
* the user types ctrl-z at the keyboard. Catch it and suspend the
* foreground job by sending it a SIGTSTP.
*
* Requires:
* SIGTSTP is sent out successfully
*
* Effects:
* Send SIGTSTP to every process in the process group of current foreground job
*/
static void
sigtstp_handler(int signum)
{
// Prevent an "unused parameter" warning.
(void)signum;
pid_t pid;
// Get pid of current foreground job
if ((pid = fgpid(jobs)) <= 0) {
return;
}
// Send SIGTSTP to every process in process group |pid|
if (kill(-pid, SIGTSTP) < 0) {
perror("kill");
}
return;
}
/*
* sigquit_handler - The driver program can gracefully terminate the
* child shell by sending it a SIGQUIT signal.
*
* Requires:
* "signum" is SIGQUIT.
*
* Effects:
* Terminates the program.
*/
static void
sigquit_handler(int signum)
{
// Prevent an "unused parameter" warning.
(void)signum;
Sio_puts("Terminating after receipt of SIGQUIT signal\n");
_exit(1);
}
/*
* This comment marks the end of the signal handlers.
*/
/*
* The following helper routines manipulate the jobs list.
*/
/*
* Requires:
* "job" points to a job structure.
*
* Effects:
* Clears the fields in the referenced job structure.
*/
static void
clearjob(JobP job)
{
job->pid = 0;
job->jid = 0;
job->state = UNDEF;
job->cmdline[0] = '\0';
}
/*
* Requires:
* "jobs" points to an array of MAXJOBS job structures.
*
* Effects:
* Initializes the jobs list to an empty state.
*/
static void
initjobs(JobP jobs)
{
int i;
for (i = 0; i < MAXJOBS; i++)
clearjob(&jobs[i]);
}
/*
* Requires:
* "jobs" points to an array of MAXJOBS job structures.
*
* Effects:
* Returns the largest allocated job ID.
*/
static int
maxjid(JobP jobs)
{
int i, max = 0;
for (i = 0; i < MAXJOBS; i++)
if (jobs[i].jid > max)
max = jobs[i].jid;
return (max);
}
/*
* Requires:
* "jobs" points to an array of MAXJOBS job structures, and "cmdline" is
* a properly terminated string.
*
* Effects:
* Adds a job to the jobs list.
*/
static int
addjob(JobP jobs, pid_t pid, int state, const char *cmdline)
{
int i;
if (pid < 1)
return (0);
for (i = 0; i < MAXJOBS; i++) {
if (jobs[i].pid == 0) {
jobs[i].pid = pid;
jobs[i].state = state;
jobs[i].jid = nextjid++;
if (nextjid > MAXJOBS)
nextjid = 1;
// Remove the "volatile" qualifier using a cast.
strcpy((char *)jobs[i].cmdline, cmdline);
if (verbose) {
printf("Added job [%d] %d %s\n", jobs[i].jid,
(int)jobs[i].pid, jobs[i].cmdline);
}
return (1);
}
}
printf("Tried to create too many jobs\n");
return (0);
}
/*
* Requires:
* "jobs" points to an array of MAXJOBS job structures.
*
* Effects:
* Deletes a job from the jobs list whose PID equals "pid".
*/
static int
deletejob(JobP jobs, pid_t pid)
{
int i;
if (pid < 1)
return (0);
for (i = 0; i < MAXJOBS; i++) {
if (jobs[i].pid == pid) {
clearjob(&jobs[i]);
nextjid = maxjid(jobs) + 1;
return (1);
}
}
return (0);
}
/*
* Requires:
* "jobs" points to an array of MAXJOBS job structures.
*
* Effects:
* Returns the PID of the current foreground job or 0 if no foreground
* job exists.
*/
static pid_t
fgpid(JobP jobs)
{
int i;
for (i = 0; i < MAXJOBS; i++)
if (jobs[i].state == FG)
return (jobs[i].pid);
return (0);
}
/*
* Requires:
* "jobs" points to an array of MAXJOBS job structures.
*
* Effects:
* Returns a pointer to the job structure with process ID "pid" or NULL if
* no such job exists.
*/
static JobP
getjobpid(JobP jobs, pid_t pid)
{
int i;
if (pid < 1)
return (NULL);
for (i = 0; i < MAXJOBS; i++)
if (jobs[i].pid == pid)
return (&jobs[i]);
return (NULL);
}
/*
* Requires:
* "jobs" points to an array of MAXJOBS job structures.
*
* Effects:
* Returns a pointer to the job structure with job ID "jid" or NULL if no
* such job exists.
*/
static JobP
getjobjid(JobP jobs, int jid)
{
int i;
if (jid < 1)
return (NULL);
for (i = 0; i < MAXJOBS; i++)
if (jobs[i].jid == jid)
return (&jobs[i]);
return (NULL);
}
/*
* Requires:
* Nothing.
*
* Effects:
* Returns the job ID for the job with process ID "pid" or 0 if no such
* job exists.
*/
static int
pid2jid(pid_t pid)
{
int i;
if (pid < 1)
return (0);
for (i = 0; i < MAXJOBS; i++)
if (jobs[i].pid == pid)
return (jobs[i].jid);
return (0);
}
/*
* Requires:
* "jobs" points to an array of MAXJOBS job structures.
*
* Effects:
* Prints the jobs list.
*/
static void
listjobs(JobP jobs)
{
int i;
for (i = 0; i < MAXJOBS; i++) {
if (jobs[i].pid != 0) {
printf("[%d] (%d) ", jobs[i].jid, (int)jobs[i].pid);
switch (jobs[i].state) {
case BG:
printf("Running ");
break;
case FG:
printf("Foreground ");
break;
case ST:
printf("Stopped ");
break;
default:
printf("listjobs: Internal error: "
"job[%d].state=%d ", i, jobs[i].state);
}
printf("%s", jobs[i].cmdline);
}
}
}
/*
* This comment marks the end of the jobs list helper routines.
*/
/*
* Other helper routines follow.
*/
/*
* Requires:
* Nothing.
*
* Effects:
* Prints a help message.
*/
static void
usage(void)
{
printf("Usage: shell [-hvp]\n");
printf(" -h print this message\n");
printf(" -v print additional diagnostic information\n");
printf(" -p do not emit a command prompt\n");
exit(1);
}
/*
* Requires:
* "msg" is a properly terminated string.
*
* Effects:
* Prints a Unix-style error message and terminates the program.
*/
static void
unix_error(const char *msg)
{
fprintf(stdout, "%s: %s\n", msg, strerror(errno));
exit(1);
}
/*
* Requires:
* "msg" is a properly terminated string.
*
* Effects: