《操作系统》的实验代码。
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254 lines
5.8 KiB

#include <ulib.h>
#include <stdio.h>
#include <string.h>
#include <dir.h>
#include <file.h>
#include <error.h>
#include <unistd.h>
#define printf(...) fprintf(1, __VA_ARGS__)
#define putc(c) printf("%c", c)
#define BUFSIZE 4096
#define WHITESPACE " \t\r\n"
#define SYMBOLS "<|>&;"
char shcwd[BUFSIZE];
int
gettoken(char **p1, char **p2) {
char *s;
if ((s = *p1) == NULL) {
return 0;
}
while (strchr(WHITESPACE, *s) != NULL) {
*s ++ = '\0';
}
if (*s == '\0') {
return 0;
}
*p2 = s;
int token = 'w';
if (strchr(SYMBOLS, *s) != NULL) {
token = *s, *s ++ = '\0';
}
else {
bool flag = 0;
while (*s != '\0' && (flag || strchr(WHITESPACE SYMBOLS, *s) == NULL)) {
if (*s == '"') {
*s = ' ', flag = !flag;
}
s ++;
}
}
*p1 = (*s != '\0' ? s : NULL);
return token;
}
char *
readline(const char *prompt) {
static char buffer[BUFSIZE];
if (prompt != NULL) {
printf("%s", prompt);
}
int ret, i = 0;
while (1) {
char c;
if ((ret = read(0, &c, sizeof(char))) < 0) {
return NULL;
}
else if (ret == 0) {
if (i > 0) {
buffer[i] = '\0';
break;
}
return NULL;
}
if (c == 3) {
return NULL;
}
else if (c >= ' ' && i < BUFSIZE - 1) {
putc(c);
buffer[i ++] = c;
}
else if (c == '\b' && i > 0) {
putc(c);
i --;
}
else if (c == '\n' || c == '\r') {
putc(c);
buffer[i] = '\0';
break;
}
}
return buffer;
}
void
usage(void) {
printf("usage: sh [command-file]\n");
}
int
reopen(int fd2, const char *filename, uint32_t open_flags) {
int ret, fd1;
close(fd2);
if ((ret = open(filename, open_flags)) >= 0 && ret != fd2) {
close(fd2);
fd1 = ret, ret = dup2(fd1, fd2);
close(fd1);
}
return ret < 0 ? ret : 0;
}
int
testfile(const char *name) {
int ret;
if ((ret = open(name, O_RDONLY)) < 0) {
return ret;
}
close(ret);
return 0;
}
int
runcmd(char *cmd) {
static char argv0[BUFSIZE];
const char *argv[EXEC_MAX_ARG_NUM + 1];
char *t;
int argc, token, ret, p[2];
again:
argc = 0;
while (1) {
switch (token = gettoken(&cmd, &t)) {
case 'w':
if (argc == EXEC_MAX_ARG_NUM) {
printf("sh error: too many arguments\n");
return -1;
}
argv[argc ++] = t;
break;
case '<':
if (gettoken(&cmd, &t) != 'w') {
printf("sh error: syntax error: < not followed by word\n");
return -1;
}
if ((ret = reopen(0, t, O_RDONLY)) != 0) {
return ret;
}
break;
case '>':
if (gettoken(&cmd, &t) != 'w') {
printf("sh error: syntax error: > not followed by word\n");
return -1;
}
if ((ret = reopen(1, t, O_RDWR | O_TRUNC | O_CREAT)) != 0) {
return ret;
}
break;
case '|':
// if ((ret = pipe(p)) != 0) {
// return ret;
// }
if ((ret = fork()) == 0) {
close(0);
if ((ret = dup2(p[0], 0)) < 0) {
return ret;
}
close(p[0]), close(p[1]);
goto again;
}
else {
if (ret < 0) {
return ret;
}
close(1);
if ((ret = dup2(p[1], 1)) < 0) {
return ret;
}
close(p[0]), close(p[1]);
goto runit;
}
break;
case 0:
goto runit;
case ';':
if ((ret = fork()) == 0) {
goto runit;
}
else {
if (ret < 0) {
return ret;
}
waitpid(ret, NULL);
goto again;
}
break;
default:
printf("sh error: bad return %d from gettoken\n", token);
return -1;
}
}
runit:
if (argc == 0) {
return 0;
}
else if (strcmp(argv[0], "cd") == 0) {
if (argc != 2) {
return -1;
}
strcpy(shcwd, argv[1]);
return 0;
}
if ((ret = testfile(argv[0])) != 0) {
if (ret != -E_NOENT) {
return ret;
}
snprintf(argv0, sizeof(argv0), "/%s", argv[0]);
argv[0] = argv0;
}
argv[argc] = NULL;
return __exec(NULL, argv);
}
int
main(int argc, char **argv) {
printf("user sh is running!!!");
int ret, interactive = 1;
if (argc == 2) {
if ((ret = reopen(0, argv[1], O_RDONLY)) != 0) {
return ret;
}
interactive = 0;
}
else if (argc > 2) {
usage();
return -1;
}
//shcwd = malloc(BUFSIZE);
assert(shcwd != NULL);
char *buffer;
while ((buffer = readline((interactive) ? "$ " : NULL)) != NULL) {
shcwd[0] = '\0';
int pid;
if ((pid = fork()) == 0) {
ret = runcmd(buffer);
exit(ret);
}
assert(pid >= 0);
if (waitpid(pid, &ret) == 0) {
if (ret == 0 && shcwd[0] != '\0') {
ret = 0;
}
if (ret != 0) {
printf("error: %d - %e\n", ret, ret);
}
}
}
return 0;
}