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