495 lines
8.1 KiB
C
495 lines
8.1 KiB
C
// Shell.
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#include "types.h"
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#include "user.h"
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#include "fcntl.h"
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// Parsed command representation
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#define EXEC 1
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#define REDIR 2
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#define PIPE 3
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#define LIST 4
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#define BACK 5
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#define MAXARGS 10
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struct cmd {
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int type;
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};
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struct execcmd {
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int type;
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char *argv[MAXARGS];
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char *eargv[MAXARGS];
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};
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struct redircmd {
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int type;
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struct cmd *cmd;
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char *file;
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char *efile;
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int mode;
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int fd;
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};
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struct pipecmd {
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int type;
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struct cmd *left;
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struct cmd *right;
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};
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struct listcmd {
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int type;
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struct cmd *left;
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struct cmd *right;
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};
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struct backcmd {
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int type;
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struct cmd *cmd;
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};
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int fork1(void); // Fork but panics on failure.
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void panic(char*);
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struct cmd *parsecmd(char*);
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// Execute cmd. Never returns.
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void
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runcmd(struct cmd *cmd)
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{
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int p[2];
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struct backcmd *bcmd;
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struct execcmd *ecmd;
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struct listcmd *lcmd;
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struct pipecmd *pcmd;
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struct redircmd *rcmd;
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if(cmd == 0)
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exit();
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switch(cmd->type){
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default:
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panic("runcmd");
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case EXEC:
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ecmd = (struct execcmd*)cmd;
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if(ecmd->argv[0] == 0)
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exit();
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exec(ecmd->argv[0], ecmd->argv);
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printf(2, "exec %s failed\n", ecmd->argv[0]);
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break;
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case REDIR:
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rcmd = (struct redircmd*)cmd;
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close(rcmd->fd);
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if(open(rcmd->file, rcmd->mode) < 0){
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printf(2, "open %s failed\n", rcmd->file);
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exit();
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}
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runcmd(rcmd->cmd);
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break;
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case LIST:
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lcmd = (struct listcmd*)cmd;
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if(fork1() == 0)
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runcmd(lcmd->left);
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wait();
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runcmd(lcmd->right);
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break;
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case PIPE:
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pcmd = (struct pipecmd*)cmd;
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if(pipe(p) < 0)
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panic("pipe");
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if(fork1() == 0){
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close(1);
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dup(p[1]);
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close(p[0]);
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close(p[1]);
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runcmd(pcmd->left);
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}
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if(fork1() == 0){
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close(0);
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dup(p[0]);
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close(p[0]);
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close(p[1]);
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runcmd(pcmd->right);
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}
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close(p[0]);
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close(p[1]);
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wait();
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wait();
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break;
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case BACK:
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bcmd = (struct backcmd*)cmd;
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if(fork1() == 0)
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runcmd(bcmd->cmd);
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break;
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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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main(void)
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{
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static char buf[100];
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int fd;
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// Assumes three file descriptors open.
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while((fd = open("console", O_RDWR)) >= 0){
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if(fd >= 3){
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close(fd);
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break;
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}
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}
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// Read and run input commands.
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while(getcmd(buf, sizeof(buf)) >= 0){
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if(buf[0] == 'c' && buf[1] == 'd' && buf[2] == ' '){
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// Clumsy but will have to do for now.
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// Chdir has no effect on the parent if run in the child.
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buf[strlen(buf)-1] = 0; // chop \n
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if(chdir(buf+3) < 0)
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printf(2, "cannot cd %s\n", buf+3);
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continue;
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}
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if(fork1() == 0)
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runcmd(parsecmd(buf));
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wait();
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}
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exit();
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}
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void
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panic(char *s)
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{
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printf(2, "%s\n", s);
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exit();
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}
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int
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fork1(void)
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{
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int pid;
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pid = fork();
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if(pid == -1)
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panic("fork");
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return pid;
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}
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//PAGEBREAK!
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// Constructors
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struct cmd*
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execcmd(void)
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{
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struct execcmd *cmd;
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cmd = malloc(sizeof(*cmd));
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memset(cmd, 0, sizeof(*cmd));
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cmd->type = EXEC;
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return (struct cmd*)cmd;
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}
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struct cmd*
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redircmd(struct cmd *subcmd, char *file, char *efile, int mode, int fd)
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{
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struct redircmd *cmd;
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cmd = malloc(sizeof(*cmd));
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memset(cmd, 0, sizeof(*cmd));
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cmd->type = REDIR;
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cmd->cmd = subcmd;
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cmd->file = file;
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cmd->efile = efile;
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cmd->mode = mode;
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cmd->fd = fd;
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return (struct cmd*)cmd;
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}
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struct cmd*
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pipecmd(struct cmd *left, struct cmd *right)
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{
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struct pipecmd *cmd;
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cmd = malloc(sizeof(*cmd));
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memset(cmd, 0, sizeof(*cmd));
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cmd->type = PIPE;
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cmd->left = left;
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cmd->right = right;
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return (struct cmd*)cmd;
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}
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struct cmd*
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listcmd(struct cmd *left, struct cmd *right)
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{
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struct listcmd *cmd;
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cmd = malloc(sizeof(*cmd));
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memset(cmd, 0, sizeof(*cmd));
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cmd->type = LIST;
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cmd->left = left;
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cmd->right = right;
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return (struct cmd*)cmd;
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}
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struct cmd*
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backcmd(struct cmd *subcmd)
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{
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struct backcmd *cmd;
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cmd = malloc(sizeof(*cmd));
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memset(cmd, 0, sizeof(*cmd));
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cmd->type = BACK;
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cmd->cmd = subcmd;
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return (struct cmd*)cmd;
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}
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//PAGEBREAK!
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// Parsing
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char whitespace[] = " \t\r\n\v";
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char symbols[] = "<|>&;()";
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int
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gettoken(char **ps, char *es, char **q, char **eq)
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{
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char *s;
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int ret;
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s = *ps;
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while(s < es && strchr(whitespace, *s))
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s++;
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if(q)
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*q = s;
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ret = *s;
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switch(*s){
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case 0:
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break;
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case '|':
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case '(':
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case ')':
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case ';':
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case '&':
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case '<':
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s++;
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break;
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case '>':
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s++;
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if(*s == '>'){
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ret = '+';
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s++;
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}
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break;
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default:
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ret = 'a';
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while(s < es && !strchr(whitespace, *s) && !strchr(symbols, *s))
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s++;
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break;
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}
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if(eq)
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*eq = s;
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while(s < es && strchr(whitespace, *s))
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s++;
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*ps = s;
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return ret;
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}
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int
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peek(char **ps, char *es, char *toks)
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{
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char *s;
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s = *ps;
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while(s < es && strchr(whitespace, *s))
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s++;
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*ps = s;
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return *s && strchr(toks, *s);
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}
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struct cmd *parseline(char**, char*);
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struct cmd *parsepipe(char**, char*);
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struct cmd *parseexec(char**, char*);
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struct cmd *nulterminate(struct cmd*);
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struct cmd*
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parsecmd(char *s)
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{
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char *es;
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struct cmd *cmd;
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es = s + strlen(s);
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cmd = parseline(&s, es);
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peek(&s, es, "");
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if(s != es){
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printf(2, "leftovers: %s\n", s);
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panic("syntax");
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}
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nulterminate(cmd);
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return cmd;
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}
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struct cmd*
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parseline(char **ps, char *es)
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{
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struct cmd *cmd;
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cmd = parsepipe(ps, es);
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while(peek(ps, es, "&")){
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gettoken(ps, es, 0, 0);
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cmd = backcmd(cmd);
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}
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if(peek(ps, es, ";")){
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gettoken(ps, es, 0, 0);
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cmd = listcmd(cmd, parseline(ps, es));
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}
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return cmd;
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}
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struct cmd*
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parsepipe(char **ps, char *es)
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{
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struct cmd *cmd;
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cmd = parseexec(ps, es);
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if(peek(ps, es, "|")){
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gettoken(ps, es, 0, 0);
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cmd = pipecmd(cmd, parsepipe(ps, es));
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}
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return cmd;
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}
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struct cmd*
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parseredirs(struct cmd *cmd, char **ps, char *es)
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{
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int tok;
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char *q, *eq;
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while(peek(ps, es, "<>")){
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tok = gettoken(ps, es, 0, 0);
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if(gettoken(ps, es, &q, &eq) != 'a')
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panic("missing file for redirection");
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switch(tok){
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case '<':
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cmd = redircmd(cmd, q, eq, O_RDONLY, 0);
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break;
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case '>':
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cmd = redircmd(cmd, q, eq, O_WRONLY|O_CREATE, 1);
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break;
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case '+': // >>
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cmd = redircmd(cmd, q, eq, O_WRONLY|O_CREATE, 1);
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break;
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}
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}
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return cmd;
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}
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struct cmd*
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parseblock(char **ps, char *es)
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{
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struct cmd *cmd;
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if(!peek(ps, es, "("))
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panic("parseblock");
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gettoken(ps, es, 0, 0);
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cmd = parseline(ps, es);
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if(!peek(ps, es, ")"))
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panic("syntax - missing )");
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gettoken(ps, es, 0, 0);
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cmd = parseredirs(cmd, ps, es);
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return cmd;
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}
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struct cmd*
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parseexec(char **ps, char *es)
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{
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char *q, *eq;
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int tok, argc;
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struct execcmd *cmd;
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struct cmd *ret;
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if(peek(ps, es, "("))
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return parseblock(ps, es);
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ret = execcmd();
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cmd = (struct execcmd*)ret;
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argc = 0;
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ret = parseredirs(ret, ps, es);
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while(!peek(ps, es, "|)&;")){
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if((tok=gettoken(ps, es, &q, &eq)) == 0)
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break;
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if(tok != 'a')
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panic("syntax");
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cmd->argv[argc] = q;
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cmd->eargv[argc] = eq;
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argc++;
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if(argc >= MAXARGS)
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panic("too many args");
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ret = parseredirs(ret, ps, es);
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}
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cmd->argv[argc] = 0;
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cmd->eargv[argc] = 0;
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return ret;
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}
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// NUL-terminate all the counted strings.
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struct cmd*
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nulterminate(struct cmd *cmd)
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{
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int i;
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struct backcmd *bcmd;
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struct execcmd *ecmd;
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struct listcmd *lcmd;
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struct pipecmd *pcmd;
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struct redircmd *rcmd;
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if(cmd == 0)
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return 0;
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switch(cmd->type){
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case EXEC:
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ecmd = (struct execcmd*)cmd;
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for(i=0; ecmd->argv[i]; i++)
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*ecmd->eargv[i] = 0;
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break;
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case REDIR:
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rcmd = (struct redircmd*)cmd;
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nulterminate(rcmd->cmd);
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*rcmd->efile = 0;
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break;
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case PIPE:
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pcmd = (struct pipecmd*)cmd;
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nulterminate(pcmd->left);
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nulterminate(pcmd->right);
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break;
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case LIST:
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lcmd = (struct listcmd*)cmd;
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nulterminate(lcmd->left);
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nulterminate(lcmd->right);
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break;
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case BACK:
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bcmd = (struct backcmd*)cmd;
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nulterminate(bcmd->cmd);
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break;
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}
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return cmd;
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}
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