[英]C executing a pipe: execlp works while execvp doesn't
Could someone explain to me why this gives the normal behavior (ls | cat) 有人可以向我解释为什么这会给出正常的行为(ls | cat)
int fd[2]; pipe(fd);
pid_t pid = fork();
if(pid > 0) {
close(fd[0]);
close(STDOUT_FILENO);
dup2(fd[1],STDOUT_FILENO);
execlp("ls","ls",NULL);
} else if (pid == 0) {
close(fd[1]);
close(STDIN_FILENO);
dup2(fd[0],STDIN_FILENO);
execlp("cat","cat",NULL);
} else {
error(1, errno, "forking error");
}
but when I change execlp to execvp suddenly nothing is output and exit status is 255? 但是当我将execlp更改为execvp时突然没有输出任何内容并退出状态为255? Code:
码:
int fd[2]; pipe(fd);
pid_t pid = fork();
if(pid > 0) {
close(fd[0]);
close(STDOUT_FILENO);
dup2(fd[1],STDOUT_FILENO);
char **args = {"ls", NULL};
execvp("ls",args);
} else if (pid == 0) {
close(fd[1]);
close(STDIN_FILENO);
dup2(fd[0],STDIN_FILENO);
char **args = {"cat", NULL};
execvp("cat",args);
} else {
error(1, errno, "forking error");
}
I'd really like to use execvp because I'll be executing commands with variable length arg lists. 我真的很想使用execvp因为我将执行带有可变长度arg列表的命令。 Help would be much appreciated.
非常感谢帮助。
char **args = {"ls", NULL};
should be char *args[] = {"ls", NULL};
应该是
char *args[] = {"ls", NULL};
, and the same for the second args
(for cat
). 和第二个
args
(对于cat
)相同。
(It's too late here, so I can't think of the reason for the first one to compile . At least it gives a warning). (现在为时已晚,所以我无法想到第一个编译的原因。至少它会发出警告)。
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