要求：
- 实现 管道 (也就是
|) - 实现 输入输出重定向(也就是
<>>>) - 实现 后台运行（也就是
&） - 实现
cd，要求支持能切换到绝对路径，相对路径和支持cd - - 屏蔽一些信号（如
ctrl + c不能终止）
1.将输入命令拆分存入二维字符指针分配的内存中
char **getcmd(int *p)
{
char **cmd = (char **)malloc(sizeof(char *) * cmdsize);
char *input = (char *)malloc(sizeof(char) * 1000);
int len = 0, count = 0, pi = 0, i = 0;
if (fgets(input, 1000, stdin) == NULL)
{
input[0] = 0;
}
int l = strlen(input);
if (l == 0)
{
free(cmd);
free(input);
exit(0);
}
if (strcmp(input, "\n") == 0)
{
cmd[0] = (char *)malloc(5);
strcpy(cmd[0], "\n");
free(input);
return cmd;
}
input[l - 1] = '\0';
// add_history(input);
while (len < l - 1)
{
while (input[len] == ' ')
{
len++;
i++;
}
while (len < l - 1 && (input[len] != ' ' && input[len] != '|' && input[len] != '>' && input[len] != '<' && input[len] != '&'))
{
if (input[len] == '&')
{
bg = 1;
input[len] = ' ';
}
len++;
}
cmd[count] = (char *)malloc(sizeof(char) * 20);
realsize++;
strncpy(cmd[count++], input + i, len - i);
cmd[count - 1][len - i] = '\0';
if (strcmp(cmd[count - 1], "~") == 0)
{
strcpy(cmd[count - 1], "/home/kangning");
}
// printf("|%s|\n",cmd[count-1]);
while (input[len] == ' ' || input[len] == '&')
{
if (input[len] == '&')
{
bg = 1;
}
len++;
}
if (input[len] == '<')
{
in = count;
len++;
}
else if (input[len] == '>')
{
len++;
if (input[len] == '>')
{
len++;
add = count;
}
else
out = count;
}
if (input[len] == '|')
{
len++;
p[pi++] = count;
}
while (input[len] == ' ' || input[len] == '<' || input[len] == '|' || input[len] == '>')
{
len++;
}
i = len;
}
free(input);
input = NULL;
return cmd;
}2.没有管道时执行这个函数
void execcmd(char **cmd)
{
pid_t pid;
int status;
pid = fork();
switch (pid)
{
case -1:
perror("fork");
return;
case 0:
if (out)
{
int fd;
if ((fd = open(cmd[out], O_RDWR | O_CREAT | O_TRUNC, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
dup2(fd, STDOUT_FILENO);
close(fd);
free(cmd[out]);
cmd[out] = NULL;
}
if (add)
{
int fd;
if ((fd = open(cmd[add], O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
lseek(fd, -1, SEEK_END);
dup2(fd, STDOUT_FILENO);
close(fd);
free(cmd[add]);
cmd[add] = NULL;
}
execvp(cmd[0], cmd);
default:
if (!bg)
mywait(pid, &status, 0);
}
}
3.有管道时执行这个函数
思路：命令用管道符号分开，分别执行，使用两个中间文件进行传输，还会用到swap函数来调换文件描述符，cutcmd函数将一维字符串分割成二维字符串
void piexec(char **cmd, int *p, int pipesize)
{
char subcmd[10][50]={};
int start = 0, i = 0, status;
pid_t ppid;
for (i = 0; i < pipesize; i++)
{
for (int j = start; j < p[i]; j++)
{
if (cmd[j])
{
strcat(subcmd[i], cmd[j]);
strcat(subcmd[i], " ");
}
}
start = p[i];
}
ppid = fork();
if (ppid == -1)
{
perror("fork");
}
else if (ppid == 0)
{
pid_t pid;
int sfd[2];
for (i = 0; i <= pipesize; i++)
{
if (i == 0)
{
if ((pid = fork()) == -1)
{
perror("fork");
}
else if (pid == 0)
{
int fd[2];
if ((fd[0] = open("fifo1", O_RDWR | O_CREAT | O_TRUNC, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
if ((fd[1] = open("fifo2", O_RDWR | O_CREAT | O_TRUNC, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
sfd[1] = dup(STDOUT_FILENO);
dup2(fd[1], STDOUT_FILENO);
char **tmp = cutcmd(subcmd[i]);
execvp(cmd[0], tmp);
}
else
{
mywait(pid, &status, 0);
dup2(sfd[1], STDOUT_FILENO);
}
}
else if (i < pipesize)
{
if ((pid = fork()) == -1)
{
perror("fork");
}
else if (pid == 0)
{
int fd[2];
if ((fd[0] = open("fifo1", O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
if ((fd[1] = open("fifo2", O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
swap(&fd[0], &fd[1]);
sfd[1] = dup(STDOUT_FILENO);
sfd[0] = dup(STDIN_FILENO);
dup2(fd[0], STDIN_FILENO);
dup2(fd[1], STDOUT_FILENO);
close(fd[0]);
close(fd[1]);
execvp(cmd[p[i]], cutcmd(subcmd[i]));
}
else
{
mywait(pid, &status, 0);
dup2(sfd[0], STDIN_FILENO);
dup2(sfd[1], STDOUT_FILENO);
}
}
else
{
if ((pid = fork()) == -1)
{
perror("fork");
}
else if (pid == 0)
{
int fd[2];
if ((fd[0] = open("fifo1", O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
if ((fd[1] = open("fifo2", O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
if (pipesize % 2)
swap(&fd[0], &fd[1]);
sfd[0] = dup(STDIN_FILENO);
int res = dup2(fd[0], STDIN_FILENO);
if (res == -1)
{
fprintf(stderr, "error dup2\n");
exit(1);
}
if (out)
{
int fd;
if ((fd = open(cmd[out], O_RDWR | O_CREAT | O_TRUNC, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
dup2(fd, STDOUT_FILENO);
close(fd);
free(cmd[out]);
cmd[out] = NULL;
}
if (add)
{
int fd;
if ((fd = open(cmd[add], O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
lseek(fd, -1, SEEK_END);
dup2(fd, STDOUT_FILENO);
close(fd);
free(cmd[add]);
cmd[add] = NULL;
}
close(fd[0]);
close(fd[1]);
printf("here\n");
execvp(cmd[start], cmd + start);
}
else
{
mywait(pid, &status, 0);
dup2(sfd[0], STDIN_FILENO);
}
}
}
}
else if (ppid > 0)
{
if (!bg)
{
mywait(ppid, &status, 0);
}
// while(1){
// sleep(1);
// printf("-");
// }
unlink("fifo1");
unlink("fifo2");
}
}
swap函数：
void swap(int *fd0, int *fd1)
{
int temp = *fd0;
*fd0 = *fd1;
*fd1 = temp;
}cutcmd函数：
char **cutcmd(char *input)
{
char **cmd = (char **)malloc(sizeof(char *) * cmdsize);
int len = 0, count = 0, pi = 0, i = 0;
int l = strlen(input);
while (len < l)
{
cmd[count] = (char *)malloc(sizeof(char) * 20);
while (len < l && (input[len] != ' '))
{
len++;
}
strncpy(cmd[count++], input + i, len - i);
if (strcmp(cmd[count - 1], "~") == 0)
{
strcpy(cmd[count - 1], "/home/kangning");
}
i = len;
while (input[len] == ' ' || input[len] == '|')
{
i++;
len++;
}
}
return cmd;
}
4.主函数循环：
int main(void)
{
sigset_t set;
sigemptyset(&set);
sigaddset(&set, SIGINT);
sigprocmask(SIG_BLOCK, &set, NULL);
setvbuf(stdout, NULL, _IONBF, 0);
last = (char *)malloc(sizeof(char) * 100);
while (1)
{
out = 0, add = 0, realsize = 0;
int p[10] = {0}, sfd, fd, pipesize = 0;
printf("# ");
char **cmd = getcmd(p);
if (strcmp(cmd[0], "\n") == 0)
{
free(cmd[0]);
cmd[0] = NULL;
free(cmd);
cmd = NULL;
continue;
}
int aaa = 0;
if (in)
{
sfd = dup(STDIN_FILENO);
fd = open(cmd[in], O_RDWR, S_IRUSR | S_IWUSR);
if (dup2(fd, STDIN_FILENO) == -1)
{
fprintf(stderr, "error dup2\n");
exit(1);
}
free(cmd[in]);
cmd[in] = NULL;
}
if (strcmp(cmd[0], "exit") == 0)
{
exit(0);
}
else if (strcmp(cmd[0], "cd") == 0)
{
if (cmd[1] && strcmp(cmd[1], "-") == 0)
{
if (last)
{
char *buf = (char *)malloc(sizeof(char) * 100);
getcwd(buf, 100);
printf("%s\n", last);
chdir(last);
strcpy(last, buf);
}
else
{ // last==NULL
printf("bash: cd: OLDPWD 未设定\n");
}
}
else
{
getcwd(last, 100);
chdir(cmd[1]);
}
continue;
}
for (int i = 0; i < 10; i++)
{
if (p[i])
pipesize++;
}
if (p[0])
{
piexec(cmd, p, pipesize);
}
else
execcmd(cmd);
if (in)
{
if (dup2(sfd, STDIN_FILENO) == -1)
{
fprintf(stderr, "error dup2\n");
}
in = 0;
}
// printf("realsize = %d\n",realsize);
for (int i = 0; i < realsize; i++)
{
if ((add && (i == add)) || (out && (i == out)) || (in && (i == in)))
continue;
free(cmd[i]);
cmd[i] = NULL;
}
free(cmd);
cmd = NULL;
}
free(last);
return 0;
}
5.全局变量解释：in 重定向输入，out 重定向输出，add 重定向追加，pipesize 管道数量，cmdsize 二维字符数组中的一维数量
6.mywait函数回收子进程
void mywait(pid_t pid, int *status, int options)
{
waitpid(pid, status, options);
if (WIFSIGNALED(*status))
{
printf("\nshell be killed by %d", WTERMSIG(*status));
if (WCOREDUMP(*status))
{
printf("\n退出 (核心已转储)");
}
}
}
7.源代码
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/fcntl.h>
#include <sys/stat.h>
#include <errno.h>
int in = 0, out = 0, add = 0, bg = 0, cmdsize = 100, realsize = 0;
char *last;
char **getcmd(int *p);
char **cutcmd(char *input);
void execcmd(char **cmd);
void swap(int *fd0, int *fd1);
void piexec(char **cmd, int *p, int pipesize);
void piexec1(char **cmd, int *p, int pipesize);
void mywait(pid_t pid, int *status, int options);
void newexec(char **cmd, int *p, int pipesize, int start, int head);
int main(void)
{
sigset_t set;
sigemptyset(&set);
sigaddset(&set, SIGINT);
sigprocmask(SIG_BLOCK, &set, NULL);
setvbuf(stdout, NULL, _IONBF, 0);
last = (char *)malloc(sizeof(char) * 100);
while (1)
{
out = 0, add = 0, realsize = 0;
int p[10] = {0}, sfd, fd, pipesize = 0;
printf("# ");
char **cmd = getcmd(p);
if (strcmp(cmd[0], "\n") == 0)
{
free(cmd[0]);
cmd[0] = NULL;
free(cmd);
cmd = NULL;
continue;
}
int aaa = 0;
if (in)
{
sfd = dup(STDIN_FILENO);
fd = open(cmd[in], O_RDWR, S_IRUSR | S_IWUSR);
if (dup2(fd, STDIN_FILENO) == -1)
{
fprintf(stderr, "error dup2\n");
exit(1);
}
free(cmd[in]);
cmd[in] = NULL;
}
if (strcmp(cmd[0], "exit") == 0)
{
exit(0);
}
else if (strcmp(cmd[0], "cd") == 0)
{
if (cmd[1] && strcmp(cmd[1], "-") == 0)
{
if (last)
{
char *buf = (char *)malloc(sizeof(char) * 100);
getcwd(buf, 100);
printf("%s\n", last);
chdir(last);
strcpy(last, buf);
}
else
{ // last==NULL
printf("bash: cd: OLDPWD 未设定\n");
}
}
else
{
getcwd(last, 100);
chdir(cmd[1]);
}
continue;
}
for (int i = 0; i < 10; i++)
{
if (p[i])
pipesize++;
}
if (p[0])
{
piexec(cmd, p, pipesize);
}
else
execcmd(cmd);
if (in)
{
if (dup2(sfd, STDIN_FILENO) == -1)
{
fprintf(stderr, "error dup2\n");
}
in = 0;
}
// printf("realsize = %d\n",realsize);
for (int i = 0; i < realsize; i++)
{
if ((add && (i == add)) || (out && (i == out)) || (in && (i == in)))
continue;
free(cmd[i]);
cmd[i] = NULL;
}
free(cmd);
cmd = NULL;
}
free(last);
return 0;
}
char **getcmd(int *p)
{
char **cmd = (char **)malloc(sizeof(char *) * cmdsize);
char *input = (char *)malloc(sizeof(char) * 1000);
int len = 0, count = 0, pi = 0, i = 0;
if (fgets(input, 1000, stdin) == NULL)
{
input[0] = 0;
}
int l = strlen(input);
if (l == 0)
{
free(cmd);
free(input);
exit(0);
}
if (strcmp(input, "\n") == 0)
{
cmd[0] = (char *)malloc(5);
strcpy(cmd[0], "\n");
free(input);
return cmd;
}
input[l - 1] = '\0';
// add_history(input);
while (len < l - 1)
{
while (input[len] == ' ')
{
len++;
i++;
}
while (len < l - 1 && (input[len] != ' ' && input[len] != '|' && input[len] != '>' && input[len] != '<' && input[len] != '&'))
{
if (input[len] == '&')
{
bg = 1;
input[len] = ' ';
}
len++;
}
cmd[count] = (char *)malloc(sizeof(char) * 20);
realsize++;
strncpy(cmd[count++], input + i, len - i);
cmd[count - 1][len - i] = '\0';
if (strcmp(cmd[count - 1], "~") == 0)
{
strcpy(cmd[count - 1], "/home/kangning");
}
// printf("|%s|\n",cmd[count-1]);
while (input[len] == ' ' || input[len] == '&')
{
if (input[len] == '&')
{
bg = 1;
}
len++;
}
if (input[len] == '<')
{
in = count;
len++;
}
else if (input[len] == '>')
{
len++;
if (input[len] == '>')
{
len++;
add = count;
}
else
out = count;
}
if (input[len] == '|')
{
len++;
p[pi++] = count;
}
while (input[len] == ' ' || input[len] == '<' || input[len] == '|' || input[len] == '>')
{
len++;
}
i = len;
}
free(input);
input = NULL;
return cmd;
}
char **cutcmd(char *input)
{
char **cmd = (char **)malloc(sizeof(char *) * cmdsize);
int len = 0, count = 0, pi = 0, i = 0;
int l = strlen(input);
while (len < l)
{
cmd[count] = (char *)malloc(sizeof(char) * 20);
while (len < l && (input[len] != ' '))
{
len++;
}
strncpy(cmd[count++], input + i, len - i);
if (strcmp(cmd[count - 1], "~") == 0)
{
strcpy(cmd[count - 1], "/home/kangning");
}
i = len;
while (input[len] == ' ' || input[len] == '|')
{
i++;
len++;
}
}
return cmd;
}
void execcmd(char **cmd)
{
pid_t pid;
int status;
pid = fork();
switch (pid)
{
case -1:
perror("fork");
return;
case 0:
if (out)
{
int fd;
if ((fd = open(cmd[out], O_RDWR | O_CREAT | O_TRUNC, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
dup2(fd, STDOUT_FILENO);
close(fd);
free(cmd[out]);
cmd[out] = NULL;
}
if (add)
{
int fd;
if ((fd = open(cmd[add], O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
lseek(fd, -1, SEEK_END);
dup2(fd, STDOUT_FILENO);
close(fd);
free(cmd[add]);
cmd[add] = NULL;
}
execvp(cmd[0], cmd);
default:
if (!bg)
mywait(pid, &status, 0);
}
}
void swap(int *fd0, int *fd1)
{
int temp = *fd0;
*fd0 = *fd1;
*fd1 = temp;
}
void mywait(pid_t pid, int *status, int options)
{
waitpid(pid, status, options);
if (WIFSIGNALED(*status))
{
printf("\nshell be killed by %d", WTERMSIG(*status));
if (WCOREDUMP(*status))
{
printf("\n退出 (核心已转储)");
}
}
}
void piexec(char **cmd, int *p, int pipesize)
{
char subcmd[10][50]={};
int start = 0, i = 0, status;
pid_t ppid;
for (i = 0; i < pipesize; i++)
{
for (int j = start; j < p[i]; j++)
{
if (cmd[j])
{
strcat(subcmd[i], cmd[j]);
strcat(subcmd[i], " ");
}
}
start = p[i];
}
ppid = fork();
if (ppid == -1)
{
perror("fork");
}
else if (ppid == 0)
{
pid_t pid;
int sfd[2];
for (i = 0; i <= pipesize; i++)
{
if (i == 0)
{
if ((pid = fork()) == -1)
{
perror("fork");
}
else if (pid == 0)
{
int fd[2];
if ((fd[0] = open("fifo1", O_RDWR | O_CREAT | O_TRUNC, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
if ((fd[1] = open("fifo2", O_RDWR | O_CREAT | O_TRUNC, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
sfd[1] = dup(STDOUT_FILENO);
dup2(fd[1], STDOUT_FILENO);
char **tmp = cutcmd(subcmd[i]);
execvp(cmd[0], tmp);
}
else
{
mywait(pid, &status, 0);
dup2(sfd[1], STDOUT_FILENO);
}
}
else if (i < pipesize)
{
if ((pid = fork()) == -1)
{
perror("fork");
}
else if (pid == 0)
{
int fd[2];
if ((fd[0] = open("fifo1", O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
if ((fd[1] = open("fifo2", O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
swap(&fd[0], &fd[1]);
sfd[1] = dup(STDOUT_FILENO);
sfd[0] = dup(STDIN_FILENO);
dup2(fd[0], STDIN_FILENO);
dup2(fd[1], STDOUT_FILENO);
close(fd[0]);
close(fd[1]);
execvp(cmd[p[i]], cutcmd(subcmd[i]));
}
else
{
mywait(pid, &status, 0);
dup2(sfd[0], STDIN_FILENO);
dup2(sfd[1], STDOUT_FILENO);
}
}
else
{
if ((pid = fork()) == -1)
{
perror("fork");
}
else if (pid == 0)
{
int fd[2];
if ((fd[0] = open("fifo1", O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
if ((fd[1] = open("fifo2", O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
if (pipesize % 2)
swap(&fd[0], &fd[1]);
sfd[0] = dup(STDIN_FILENO);
int res = dup2(fd[0], STDIN_FILENO);
if (res == -1)
{
fprintf(stderr, "error dup2\n");
exit(1);
}
if (out)
{
int fd;
if ((fd = open(cmd[out], O_RDWR | O_CREAT | O_TRUNC, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
dup2(fd, STDOUT_FILENO);
close(fd);
free(cmd[out]);
cmd[out] = NULL;
}
if (add)
{
int fd;
if ((fd = open(cmd[add], O_RDWR | O_CREAT, S_IWUSR | S_IRUSR)) == -1)
{
perror("open");
}
lseek(fd, -1, SEEK_END);
dup2(fd, STDOUT_FILENO);
close(fd);
free(cmd[add]);
cmd[add] = NULL;
}
close(fd[0]);
close(fd[1]);
printf("here\n");
execvp(cmd[start], cmd + start);
}
else
{
mywait(pid, &status, 0);
dup2(sfd[0], STDIN_FILENO);
}
}
}
}
else if (ppid > 0)
{
if (!bg)
{
mywait(ppid, &status, 0);
}
// while(1){
// sleep(1);
// printf("-");
// }
unlink("fifo1");
unlink("fifo2");
}
}
写在最后：程序还有一些不完善的地方，不过还能忍，可以接受