340 lines
7.2 KiB
C
340 lines
7.2 KiB
C
#include "types.h"
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#include "stat.h"
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#include "user.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 MAXIO 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 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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struct ionode iolist[MAXIO];
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struct ionode *io;
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};
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struct cmd cmdlist[MAXCMD];
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struct cmd *cmd;
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char buf[BUFSIZ];
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int debug;
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int parse(char *s);
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void runcmd(void);
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int getcmd(char *buf, int nbuf);
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int ioredirection(struct ionode *iolist, int nio);
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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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int
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main(void)
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{
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while(getcmd(buf, sizeof(buf)) >= 0) {
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if(parse(buf) >= 0)
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runcmd();
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}
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exit();
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}
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int
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getcmd(char *buf, int nbuf)
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{
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printf(2, "$ ");
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memset(buf, 0, nbuf);
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gets(buf, nbuf);
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if(buf[0] == 0) // EOF
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return -1;
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return 0;
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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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cmd = &cmdlist[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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cmdlist[i].io = cmdlist[i].iolist;
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}
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for(;;){
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switch((c = gettoken(0, &t))) {
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case 'w': // Add an argument
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if(cmd->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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cmd->argv[cmd->argc++] = t;
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break;
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case '>': // Input and output redirection
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case '<':
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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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if(cmd->io - cmd->iolist >= MAXIO) {
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printf(2, "too many redirections\n");
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return -1;
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}
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cmd->io->token = c;
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cmd->io->s = t;
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cmd->io++;
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break;
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case ';': // command sequence
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case '|': // pipe
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if(cmd->io - cmd->iolist >= MAXIO) {
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printf(2, "too many redirections\n");
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return -1;
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}
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cmd->token = c;
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cmd++;
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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 i, r, pid, tfd;
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int fdarray[2];
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struct cmd *c;
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struct ionode *io;
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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 = &cmdlist[0]; c <= cmd; 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(c->argv[0][0] != '/') {
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c->argv0buf[0] = '/';
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strcpy(c->argv0buf + 1, c->argv[0]);
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c->argv[0] = c->argv0buf;
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}
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c->argv[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; c->argv[i]; i++)
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printf(2, " %s", c->argv[i]);
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for(io = c->iolist; io <= c->io; io++) {
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printf(2, "%c %s", io->token, io->s);
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}
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printf(2, "\n");
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}
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if(strcmp(c->argv[0], "/cd") == 0) {
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if(debug)
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printf (2, "/cd %s is build in\n", c->argv[1]);
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chdir(c->argv[1]);
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return;
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}
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if(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(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 > 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(c->iolist, c->io - c->iolist) < 0)
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exit();
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if((r = exec(c->argv0buf, (char**) c->argv)) < 0) {
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printf(2, "exec %s: %d\n", 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 > 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(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(struct ionode *iolist, int nio)
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{
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int fd;
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struct ionode *io;
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for(io = iolist; io < &iolist[nio]; io++) {
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switch(io->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(io->s, O_RDONLY)) < 0) {
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printf(2, "failed to open %s for read: %d", io->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", io->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(io->s, O_WRONLY|O_CREATE)) < 0) {
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printf(2, "failed to open %s for write: %d", io->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", io->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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// 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 0\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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