Question

我在C中创建了一个类似终端shell的程序，这是我在课堂上的练习。如果添加'＆amp;'，该程序允许同时运行多个进程在句末。（例如：$ gedit＆amp;）;但是，我的代码只是在子进程退出时运行父进程。

#include  <stdio.h>
#include  <sys/types.h>
#include <string.h>

void  parse(char *line, char **argv)
{
     while (*line != '\0') {       /* if not the end of line ....... */ 
          while (*line == ' ' || *line == '\t' || *line == '\n')
              *line++ = '\0';     /* replace white spaces with 0    */

          *argv++ = line;          /* save the argument position     */
          while (*line != '\0' && *line != ' ' && 
                 *line != '\t' && *line != '\n') 
               line++;             /* skip the argument until ...    */
     }
     *argv = '\0';                 /* mark the end of argument list  */
}


void  execute(char **argv)
{
     pid_t  pid;
     int    status;

     if ((pid = fork()) < 0) {     /* fork a child process           */
          printf("*** ERROR: forking child process failed\n");
          exit(1);
     }
     else if (pid == 0) {          /* for the child process:         */
          if (execvp(*argv, argv) < 0) {     /* execute the command  */
               printf("*** ERROR: exec failed\n");
               exit(1);
          }
     }
     else {                                  /* for the parent:      */
            wait(NULL);                          /* wait for completion  */

     }
}

void  main(void)
{
     char  line[1024];             /* the input line                 */
     char  *argv[64];              /* the command line argument      */

     while (1) {                   /* repeat until done ....         */
          printf("COMMAND -> ");     /*   display a prompt             */
          gets(line);              /*   read in the command line     */
          printf("\n");
          parse(line, argv);       /*   parse the line               */
          if (strcmp(argv[0], "exit") == 0)  /* is it an "exit"?     */
               exit(0);            /*   exit if it is                */
          execute(argv);           /* otherwise, execute the command */
     }
}

我想结果如下：

Ex：$ gedit＆amp; //使用pid = 4789运行程序gedit

$ emacs //程序emacs使用pid = 5123 ppid = 4789

运行

Answer 1

如果您看到＆符号，请忽略wait()：

void  execute(char **argv, int block)
{
     pid_t  pid;
     int    status;

     if ((pid = fork()) < 0) {
          printf("*** ERROR: forking child process failed\n");
          exit(1);
     }
     else if (pid == 0) {
          if (execvp(*argv, argv) < 0) {
               printf("*** ERROR: exec failed\n");
               exit(1);
          }
     }
     else if (block) {
            wait(NULL);
     }
}

如何在C中同时运行2个进程？

1 个答案: