Posted on 2007-08-28 15:37
ZelluX 阅读(630)
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C/C++
CSAPP上的例子，但是书中的源码有问题，修改后的版本：
#include "csapp.h"
#define MAXARGS 128
void eval(char *cmdline);
int parseline(char *buf, char **argv);
int buildin_command(char **argv);
int main()
{
char cmdline[MAXLINE];
while (1)
{
printf("> ");
Fgets(cmdline, MAXLINE, stdin);
if (feof(stdin))
exit(0);
eval(cmdline);
}
}
void eval(char *cmdline)
{
char *argv[MAXARGS];
char buf[MAXLINE];
int bg;
pid_t pid;
strcpy(buf, cmdline);
bg = parseline(buf, argv);
if (argv[0] == NULL)
return;
if (!builtin_command(argv))
{
if ((pid = Fork()) == 0)
{
if (execve(argv[0], argv, environ) < 0)
{
printf("%s: Command not found.\n", argv[0]);
exit(0);
}
}
if (!bg)
{
int status;
if (waitpid(pid, &status, 0) < 0)
unix_error("waitfg: waitpid error");
}
else
printf("%d %s", pid, cmdline);
}
return;
}
int builtin_command(char **argv)
{
if (!strcmp(argv[0], "quit"))
exit(0);
if (!strcmp(argv[0], "&"))
return 1;
return 0;
}
int parseline(char *buf, char **argv)
{
char *delim;
int argc;
int bg;
buf[strlen(buf) - 1] = ' ';
while (*buf && (*buf == ' '))
buf++;
argc = 0;
while ((delim = strchr(buf, ' ')))
{
argv[argc++] = buf;
*delim = '\0';
buf = delim + 1;
while (*buf && (*buf == ' '))
buf++;
}
argv[argc] = NULL;
if (argc == 0)
return 1;
if ((bg = (*argv[argc - 1] == '&')) != 0)
argv[--argc] = NULL;
return bg;
}