我努力让自己在C,其执行控制台shell命令不能用C叉和管
猫log.txt的程序执行控制台命令| awk'{print $ 7}'|头-10
但第三个命令不会与2目前工作。 这是我做的
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
int main()
{
int fd[2], status;
pipe(fd);
pid_t pid1 = fork();
if (!pid1)
{
dup2(fd[1], 1);
close(fd[0]);
close(fd[1]);
char* command[3] = {"/bin/cat", "log.txt", 0};
execvp(command[0], command);
exit(EXIT_FAILURE);
}
else if (pid1 == -1)
{
fprintf(stderr, "Can't fork, exiting...\n");
exit(EXIT_FAILURE);
}
pid_t pid2 = fork();
if (!pid2) {
dup2(fd[0], 0);
close(fd[0]);
close(fd[1]);
char* command[3] = {"awk", "{ print $7 }", 0};
execvp(command[0], command);
exit(EXIT_FAILURE);
} else if (pid2 == -1) {
fprintf(stderr, "Can't fork, exiting...\n");
exit(EXIT_FAILURE);
}
pid_t pid3 = fork();
if (!pid3) {
dup2(fd[0], 0);
close(fd[0]);
close(fd[1]);
char* command[3] = {"head", "-10", 0};
execvp(command[0], command);
exit(EXIT_FAILURE);
} else if (pid3 == -1) {
fprintf(stderr, "Can't fork, exiting...\n");
exit(EXIT_FAILURE);
}
close(fd[0]);
close(fd[1]);
waitpid(pid1, NULL, 0);
waitpid(pid2, NULL, 0);
waitpid(pid3, &status, 0);
exit(status);
return 0;
}
pid3无法执行。我试图在pid3中制作dup2(fd [1],1),但那是行不通的。应该在pid3上做些什么,以及如何使用dup2制作超过3个命令?
你的预期结果是什么?你观察到什么? – HAL
失去[无用的'cat'](http://partmaps.org/era/unix/award.html)似乎是一个解决方法( - : – tripleee