#include <sys/types.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
int pipFd[1000][2], hasPipe, forked, pipNum = 0, pNum = 0, bPipe = 0, bpipFd[2], stPipe, InpToChld = 0;
pid_t pid[1000];
void * outInp;
int builtin_command(char **argv)
{
if (!strcmp(argv[0], "quit")) /* quit command */
exit(0);
if (!strcmp(argv[0], "&")) /* Ignore singleton & */
return 1;
return 0; /* Not a builtin command */
}
int parsecmd(char *buf, char **argv)
{
char *delim; /* Points to first space delimiter */
int argc; /* Number of args */
int bg; /* Background job? */
buf[strlen(buf) - 1] = ' '; /* Replace trailing '\n' with space */
while (*buf && (*buf == ' ')) /* Ignore leading spaces */
buf++;
/* Build the argv list */
argc = 0;
while ((delim = strchr(buf, ' ')))
{
argv[argc++] = buf;
*delim = '\0';
buf = delim + 1;
while (*buf && (*buf == ' ' || *buf == '<')) /* Ignore spaces */
buf++;
}
argv[argc] = NULL;
if (argc == 0) /* Ignore blank line */
return 1;
/* Should the job run in the background? */
if ((bg = (*argv[argc - 1] == '&')) != 0)
argv[--argc] = NULL;
return argc;
}
void myExec(char **argv, char *buf)
{
// if ((pid[pNum] = fork()) == 0)
// {
strcpy(buf, "/bin/");
buf[5] = 0;
strcat(buf, argv[0]);
//printf("%s\n", buf);
if (execv(buf, argv) < 0)
{
memset(buf, 0, 255);
strcpy(buf, "/usr/bin/");
strcat(buf, argv[0]);
if (execv(buf, argv) < 0)
{
printf("exec failed\n");
exit(-1);
}
}
exit(0);
// }
// else
// wait(NULL);
}
int splitPipe(char **cmdLine)
{
static char *svBuftok;
if (!hasPipe)
*cmdLine = strtok_r(*cmdLine, "|", &svBuftok);
else{
//printf("--------%s\n", svBuftok);
*cmdLine = strtok_r(svBuftok, "|", &svBuftok);
}
//printf(".......................%s %s\n", svBuftok, *cmdLine);
return strlen(svBuftok);
}
int isDigit(char * strings){
int i, tmp = strlen(strings);
for(i = 0; i < tmp; i++){
if(strings[i] < '0' || strings[i] > '9') return 0;
}
return 1;
}
void handler(int sig)
{
if (sig == SIGINT && forked) exit(0);
}
static char *getcmd()
{
static char buf[256];
//fputs("> ", stdout);
//printf("asdfasdfasdf\n");
fflush(stdin);
fflush(stdout);
if (fgets(buf, sizeof(buf), stdin) == NULL)
return NULL;
if (buf[strlen(buf)] == '\n')
buf[strlen(buf)] = 0;
return buf;
}
int main()
{
char *cmdline;
char *argv[12000];
char c, dir[256], buf[256], rdBuf[100000], pipBuf[100000];
int status, fd, rfd, dest, argc;
pid_t tmpPid;
getcwd(dir, 256);
signal(SIGINT, handler);
signal(SIGTSTP, handler);
signal(SIGCHLD, handler);
signal(30, handler);
//outInp = &&Outinp;
//printf("gd\n");
while (cmdline = getcmd())
{
ret:
do
{
rfd = 0;
hasPipe = splitPipe(&cmdline);
//printf(":::::::::::::::%s %d\n", cmdline, hasPipe);
if (strlen(cmdline) <= 1)
continue;
argc = parsecmd(cmdline, argv);
if (!builtin_command(argv))
{
if(!strcmp(argv[0], "exit")) exit(0);
{
if(hasPipe) pipe(pipFd[pNum]);
if(!bPipe) pipe(bpipFd);
fflush(NULL);
if((pid[pNum] = fork()) == 0){
int ofd, svStdout = dup(1), svStin = dup(0);
forked = 1;
close(pipFd[pNum][0]);
//printf("%s %d\n",argv[0], getpid());
//fflush(stdout);
//printf("\n");
if(bPipe) {
close(pipFd[pNum - 1][1]);
dup2(pipFd[pNum - 1][0], STDIN_FILENO);
}
else{
close(bpipFd[1]);
dup2(bpipFd[0], STDIN_FILENO);
}
//addArgv(pipBuf, &argc, argv);
if(hasPipe) dup2(pipFd[pNum][1], 1);
if(!strcmp(argv[argc - 2], ">")){
//printf("chked %s\n", argv[argc - 1]);
remove(argv[argc - 1]);
ofd = open(argv[argc - 1], O_WRONLY | O_CREAT, 0755);
dup2(ofd, 1);
argc -= 2;
argv[argc] = NULL;
}
else if(!strcmp(argv[argc - 2], ">>")){
//printf("chked %s\n", argv[argc - 1]);
ofd = open(argv[argc - 1], O_WRONLY);
dup2(ofd, 1);
argc -= 2;
argv[argc] = NULL;
}
fflush(stdout);
myExec(argv, buf);
close(pipFd[pNum][1]);
if(bPipe) {
close(pipFd[pNum - 1][0]);
}
else{
close(bpipFd[0]);
}
dup2(svStin, 0);
dup2(svStdout, 1);
if(!strcmp(argv[argc - 2], ">")) close(ofd);
exit(0);
}
else{
if(!bPipe) {
close(bpipFd[0]);
stPipe = pid[pNum];
InpToChld = 1;
}
pNum++;
}
}
bPipe = hasPipe;
}
}while (hasPipe);
while(InpToChld){
memset(rdBuf, 0, sizeof(rdBuf)); int i;
fflush(NULL);
//printf("Inp~~\n");
if(read(0, rdBuf, sizeof(rdBuf)) == 0){
write(bpipFd[1], "\0", 1);
InpToChld = 0;
break;
}
if(write(bpipFd[1], rdBuf, strlen(rdBuf)) < 0){
cmdline = rdBuf;
InpToChld = 0;
goto ret;
}
fflush(NULL);
//fflush(stdout);
}
}
}
起初，执行exec尾部效果很好。
但是直到父进程死后才打印出tail的输出。
例如cat < /proc/meminfo | head效果很好
但是在退出父级之后会打印cat < /proc/meminfo | tail。
我想这与输入/输出问题有关，但我无法解决此问题。
答案 0 :(得分：0)
编写小外壳程序的步骤：
SIGCHLD redirect pipe 以下code可以工作，不能处理内置命令：
#include <ctype.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
void signal_SIGCHLD_handle(int sig) {
while (waitpid(-1, NULL, WNOHANG) > 0)
;
}
int main()
{
char buf[256];
while (fgets(buf, sizeof(buf), stdin) != NULL) {
if (fork() > 0) { // parent
wait(NULL);
continue;
}
//child
// handle SIGCHLD
struct sigaction act;
act.sa_handler = signal_SIGCHLD_handle;
sigemptyset(&act.sa_mask);
act.sa_flags = SA_RESTART;
sigaction(SIGCHLD, &act, NULL);
if (buf[strlen(buf)] == '\n')
buf[strlen(buf)] = '\0';
for (char* next_cmd = strtok(buf, "|"); next_cmd != NULL; ) {
char* current_cmd = next_cmd;
next_cmd = strtok(NULL, "|");
char* argv[10];
int argv_index = 0;
int new_argv = 1;
for (;;) {
if(*current_cmd == '\0') {
argv[argv_index] = NULL;
break;
}
if (isspace(*current_cmd)) {
*current_cmd++ = '\0';
new_argv = 1;
continue;
}
if (*current_cmd == '<') {
++current_cmd;
while (isspace(*current_cmd))
++current_cmd;
if (*current_cmd == '\0') {
printf("Please use cmd < file_name");
return -1;
}
char* filename = current_cmd;
while (!isspace(*current_cmd) && *current_cmd != '\0')
++current_cmd;
if (*current_cmd != '\0')
*current_cmd++ = '\0';
int fd = open(filename, O_RDONLY);
if (fd < 0) {
perror("<");
return -1;
}
dup2(fd, 0);
close(fd);
continue;
}
if (*current_cmd == '>') {
int add = 0;
if (*++current_cmd == '>') {
add = 1;
++current_cmd;
}
while (isspace(*current_cmd))
++current_cmd;
if (*current_cmd == '\0') {
printf(add == 0 ? "Please use cmd > file_name" : "Please use cmd >> file_name");
return -1;
}
char* filename = current_cmd;
while (!isspace(*current_cmd) && *current_cmd != '\0')
++current_cmd;
if (*current_cmd != '\0')
*current_cmd++ = '\0';
int fd = open(filename, add == 0 ? (O_WRONLY|O_CREAT) : (O_WRONLY|O_CREAT|O_APPEND), 0644);
if (fd < 0) {
perror(add == 0 ? ">" : ">>");
return -1;
}
dup2(fd, 1);
close(fd);
continue;
}
if (new_argv == 1) {
new_argv = 0;
argv[argv_index++] = current_cmd;
}
++current_cmd;
}
if (argv_index == 0)
continue;
if (next_cmd != NULL) {
int pipe_fd[2];
pipe(pipe_fd);
if (fork() == 0) {
close(pipe_fd[0]);
dup2(pipe_fd[1], STDOUT_FILENO);
close(pipe_fd[1]);
execvp(argv[0], argv);
return -1;
}
close(pipe_fd[1]);
dup2(pipe_fd[0], STDIN_FILENO);
close(pipe_fd[1]);
continue;
}
execvp(argv[0], argv);
}
}
return 0;
}