xv6-cs450/sh.c

300 lines
5.6 KiB
C
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#include "types.h"
#include "stat.h"
#include "user.h"
#include "fs.h"
#include "fcntl.h"
#define BUFSIZ 512
#define MAXARGS 10
#define MAXNODE 2
// only allocate nodes for i/o redir; at some point we may have to build a
// a real parse tree.
struct node {
int token;
char *s;
};
struct node list[MAXNODE];
int nextnode;
char buf[BUFSIZ];
char *argv[MAXARGS];
char argv0buf[BUFSIZ];
int argc;
int debug = 0;
int parse(char *s);
void runcmd(void);
int ioredirection(void);
int gettoken(char *s, char **token);
int _gettoken(char *s, char **p1, char **p2);
void addnode(int token, char *s);
int
main(void)
{
while(1){
puts("$ ");
memset (buf, '\0', sizeof(buf));
gets(buf, sizeof(buf));
if (parse(buf) < 0)
continue;
runcmd();
}
}
int
parse(char *s)
{
char *t;
int c;
gettoken(s, 0);
argc = 0;
nextnode = 0;
while (1) {
switch ((c = gettoken(0, &t))) {
case 'w': // Add an argument
if (argc == MAXARGS) {
printf(2, "too many arguments\n");
return -1;
}
argv[argc++] = t;
break;
case '<': // Input redirection
// Grab the filename from the argument list
if (gettoken(0, &t) != 'w') {
printf(2, "syntax error: < not followed by word\n");
return -1;
}
addnode('<', t);
break;
case '>': // Output redirection
// Grab the filename from the argument list
if (gettoken(0, &t) != 'w') {
printf(2, "syntax error: > not followed by word\n");
return -1;
}
addnode('>', t);
break;
case 0: // String is complete
return 0;
default:
printf(2, "syntax error: bad return %d from gettoken", c);
return -1;
}
}
}
void
runcmd(void)
{
int i, r, pid;
// Return immediately if command line was empty.
if(argc == 0) {
if (debug)
printf(2, "EMPTY COMMAND\n");
return;
}
// Clean up command line.
// Read all commands from the filesystem: add an initial '/' to
// the command name.
// This essentially acts like 'PATH=/'.
if (argv[0][0] != '/') {
argv0buf[0] = '/';
strcpy(argv0buf + 1, argv[0]);
argv[0] = argv0buf;
}
argv[argc] = 0;
// Print the command.
if (debug) {
printf(2, "[%d] SPAWN:", getpid());
for (i = 0; argv[i]; i++)
printf(2, " %s", argv[i]);
for (i = 0; i < nextnode; i++) {
printf(2, "%c %s", list[i].token, list[i].s);
}
printf(2, "\n");
}
if (strcmp(argv[0], "/cd") == 0) {
if (debug) printf (2, "/cd %s is build in\n", argv[1]);
chdir(argv[1]);
return;
}
pid = fork();
if (pid == 0) {
if (ioredirection() < 0)
exit();
if ((r = exec(argv0buf, (char**) argv)) < 0) {
printf(2, "exec %s: %d\n", argv[0], r);
exit();
}
}
if (pid > 0) {
if (debug)
printf(2, "[%d] WAIT %s\n", getpid(), argv[0]);
wait();
if (debug)
printf(2, "[%d] wait finished\n", getpid());
}
}
int
ioredirection(void)
{
int i, fd, dfd;
for (i = 0; i < nextnode; i++) {
switch (list[i].token) {
case '<':
if ((fd = open(list[i].s, O_RDONLY)) < 0) {
printf(2, "failed to open %s for read: %d", list[i].s, fd);
return -1;
}
if (debug)
printf(2, "redirect 0 from %s\n", list[i].s);
close(0);
if ((dfd = dup(fd)) < 0)
printf(2, "dup failed\n");
if (debug)
printf(2, "dup returns %d\n", dfd);
close(fd);
break;
case '>':
if ((fd = open(list[i].s, O_WRONLY|O_CREATE)) < 0) {
printf(2, "failed to open %s for write: %d", list[i].s, fd);
exit();
}
if (debug)
printf(2, "redirect 1 to %s\n", list[i].s);
if (close(1) < 0)
printf(2, "close 1 failed\n");
if ((dfd = dup(fd)) < 0)
printf(2, "dup failed\n");
if (debug)
printf(2, "dup returns %d\n", dfd);
close(fd);
break;
}
}
return 0;
}
void
addnode(int token, char *s)
{
if (nextnode >= MAXNODE) {
printf(2, "addnode: ran out of nodes\n");
return;
}
list[nextnode].token = token;
list[nextnode].s = s;
nextnode++;
}
// gettoken(s, 0) prepares gettoken for subsequent calls and returns 0.
// gettoken(0, token) parses a shell token from the previously set string,
// null-terminates that token, stores the token pointer in '*token',
// and returns a token ID (0, '<', '>', '|', or 'w').
// Subsequent calls to 'gettoken(0, token)' will return subsequent
// tokens from the string.
int
gettoken(char *s, char **p1)
{
static int c, nc;
static char* np1, *np2;
if (s) {
nc = _gettoken(s, &np1, &np2);
return 0;
}
c = nc;
*p1 = np1;
nc = _gettoken(np2, &np1, &np2);
return c;
}
// Get the next token from string s.
// Set *p1 to the beginning of the token and *p2 just past the token.
// Returns
// 0 for end-of-string;
// < for <;
// > for >;
// | for |;
// w for a word.
//
// Eventually (once we parse the space where the \0 will go),
// words get nul-terminated.
#define WHITESPACE " \t\r\n"
#define SYMBOLS "<|>&;()"
int
_gettoken(char *s, char **p1, char **p2)
{
int t;
if (s == 0) {
if (debug > 1)
printf(2, "GETTOKEN NULL\n");
return 0;
}
if (debug > 1)
printf(2, "GETTOKEN: %s\n", s);
*p1 = 0;
*p2 = 0;
while (strchr(WHITESPACE, *s))
*s++ = 0;
if (*s == 0) {
if (debug > 1)
printf(2, "EOL\n");
return 0;
}
if (strchr(SYMBOLS, *s)) {
t = *s;
*p1 = s;
*s++ = 0;
*p2 = s;
if (debug > 1)
printf(2, "TOK %c\n", t);
return t;
}
*p1 = s;
while (*s && !strchr(WHITESPACE SYMBOLS, *s))
s++;
*p2 = s;
if (debug > 1) {
t = **p2;
**p2 = 0;
printf(2, "WORD: %s\n", *p1);
**p2 = t;
}
return 'w';
}