Lab1主要是了解并运行RiscV版本的XV6，并为其添加一些用户态程序
使用make qemu运行xv6，并运行ls等程序
调用内核sleep系统调用完成功能
#include "kernel/types.h"
#include "user.h"
int
main(int argc, char *argv[]) {
int time;
if (argc != 2) {
fprintf(2, "Usage: sleep time\n\n");
exit(1);
}
time = atoi(argv[1]);
sleep(time);
exit(0);
}在Makefile的UPROGS中添加$U/_sleep\
创建一对父子进程，该对进程使用管道通信
#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
int
main() {
int p2c[2], c2p[2];
int child_id;
char *ping = "ping";
char *pong = "pong";
char buf[512] = {0};
pipe(p2c);
pipe(c2p);
child_id = fork();
if (child_id != 0) {
//parent
close(p2c[0]);
close(c2p[1]);
write(p2c[1], ping, strlen(ping));
//wait((int *)0);
read(c2p[0], buf, sizeof(buf));
printf("%d: received %s\n", getpid(), buf);
exit(0);
} else {
//child
close(p2c[1]);
close(c2p[0]);
read(p2c[0], buf, sizeof(buf));
printf("%d: received %s\n", getpid(), buf);
write(c2p[1], pong, strlen(pong));
exit(0);
}
}使用pipe、fork组成一管道过滤器，第一个进程输出2，并过滤2-35中2的倍数的数，第二个进程输出3并过滤3的倍数的数...
首先main函数初始管道，将2-35写入管道，并关闭写管道，调用filter函数处理，filter函数用于递归处理该问题，参数为上一层管道数组，从管道读端读入上一层的数字，并创建一个新管道，对数字过滤后传入下一层，下一层即为通过fork创建的子进程
#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
void
filter(int lpipe[])
{
int rpipe[2];
pipe(rpipe);
int primes[50];
int cnt = 0;
char buf[1];
while ((read(lpipe[0], buf, sizeof(buf))) != 0) {
primes[cnt++] = buf[0];
}
close(lpipe[0]);
if (cnt == 0) return;
int first = primes[0];
printf("prime %d\n", first);
for (int i = 1; i < cnt; i++) {
if (primes[i] % first != 0) {
char p = primes[i];
write(rpipe[1], &p, 1);
}
}
close(rpipe[1]);
int pid = fork();
if (pid == 0) {
//child
filter(rpipe);
}
}
int
main()
{
int lpipe[2];
pipe(lpipe);
for (int i = 2; i <= 35; i++) {
char p = i;
write(lpipe[1], &p, 1);
}
close(lpipe[1]);
filter(lpipe);
wait((int *) 0);
exit(0);
}
在一个目录树中搜索特定名称的所有文件
递归搜索目录中的指定文件即可，增加了.、*的通配符功能，正则匹配代码参考自LeetCode 44题
#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
#include "kernel/fs.h"
// int
// match(char *filename, char *name) {
// return strcmp(filename, name) == 0;
// }
// '.' Matches any single character.
// '*' Matches zero or more of the preceding element.
int match(char* s, char* p) {
if (!*p) return !*s;
if (*(p + 1) != '*')
return *s == *p || (*p == '.' && *s != '\0') ? match(s + 1, p + 1) : 0;
else
return *s == *p || (*p == '.' && *s != '\0') ? match(s, p + 2) || match(s + 1, p) : match(s, p + 2);
//return (*s == *p || (*p == '.' && *s != '\0')) && match(s + 1, p) || match(s, p + 2);
}
void
catdir(char *predix, char *name, char *buf)
{
memcpy(buf, predix, strlen(predix));
char *p = buf + strlen(predix);
*p++ = '/';
memcpy(p, name, strlen(name));
p += strlen(name);
*p++ = 0;
}
void
find(int fd, char *dir, char *name) {
struct dirent de;
while(read(fd, &de, sizeof(de)) == sizeof(de)) {
if (strcmp(de.name, ".") == 0 || strcmp(de.name, "..") == 0)
continue;
struct stat st;
char path[512];
catdir(dir, de.name, path);
if(de.inum == 0)
continue;
if(stat(path, &st) < 0){
printf("find: cannot stat %s\n", path);
continue;
}
if (st.type == T_FILE && match(de.name, name)) {
printf("%s\n", path);
} else if (st.type == T_DIR) {
int subfd;
if((subfd = open(path, 0)) < 0){
printf("find: cannot open %s\n", path);
continue;
}
find(subfd, path, name);
}
}
}
int
main(int argc, char *argv[])
{
if (argc != 3) {
fprintf(2, "Usage: find dir name\n");
exit(1);
}
char dir[DIRSIZ + 1];
char name[DIRSIZ + 1];
if (strlen(argv[1]) > DIRSIZ || strlen(argv[2]) > DIRSIZ) {
fprintf(2, "dir or name too long...\n");
exit(1);
}
memcpy(dir, argv[1], strlen(argv[1]));
memcpy(name, argv[2], strlen(argv[2]));
int fd;
struct stat st;
if((fd = open(dir, 0)) < 0){
fprintf(2, "find: cannot open %s\n", dir);
exit(1);
}
if(fstat(fd, &st) < 0){
fprintf(2, "find: cannot stat %s\n", dir);
close(fd);
exit(1);
}
if (st.type != T_DIR) {
printf("%s is not a dir\n", dir);
} else {
find(fd, dir, name);
}
exit(0);
}
编写一简单版本的UNIX xargs程序，该程序从标准输入中读取多行并将每一行作为一指定程序的参数
xargs从标准输入中读多行，多行按照\n分隔，使用exec系统调用创建子进程执行指定程序，并将标准输入读的参数和该程序原本的参数一并作为该程序参数
#include "kernel/types.h"
#include "user/user.h"
#include "kernel/fcntl.h"
#include "kernel/param.h"
#define MAX_ARG_LEN 512
void
copy_argv(char **ori_argv, int ori_argc, char *new_argv, char **argv)
{
int k = 0;
for (int i = 0; i < ori_argc; i++) {
argv[k] = malloc(strlen(ori_argv[i]) + 1);
memcpy(argv[k++], ori_argv[i], strlen(ori_argv[i]) + 1);
}
argv[k] = malloc(strlen(new_argv) + 1);
memcpy(argv[k++], new_argv, strlen(new_argv) + 1);
}
void
print(char **s, int n)
{
for (int i = 0; i < n; i++) {
printf("%s\n", s[i]);
}
}
int
main(int argc, char *argv[])
{
if (argc <= 1) {
fprintf(2, "Usage: xargx command [arg ...]\n");
exit(1);
}
char param[MAX_ARG_LEN];
int i = 0;
char ch;
int ignore = 0;
while (read(0, &ch, 1) > 0) {
if (ch == '\n') {
if (ignore) {
i = 0;
ignore = 0;
continue;
}
param[i] = 0;
i = 0;
int pid = fork();
if (pid == 0) {
//child
int cmd_argc = argc;
char *cmd_argv[MAXARG];
copy_argv(argv + 1, argc - 1, param, cmd_argv);
cmd_argv[cmd_argc] = 0;
exec(cmd_argv[0], cmd_argv);
exit(0);
} else {
wait((int *)0);
}
} else {
if (!ignore && i >= MAX_ARG_LEN - 1) {
printf("xargs: too long arguments...\n");
ignore = 1;
}
if (!ignore) {
param[i++] = ch;
}
}
}
exit(0);
}
