我正在尝试创建一个可以处理具有多个管道和输入/输出重定向的命令的shell。管道大部分都在工作，但问题出在我输入的时候：
ls | more | wc
or
ls | more | wc > output.txt
输出是：
[linux]$ ./a.out
shell> ls | more | wc <---- I entered the command here
In Child executing 0
First Child executing 0
In Child executing 2
Last Child executing 2
In Child executing 1
Middle Child executing 1
shell> 20 20 137 <----- The output is on the shell command line
<------ The cursor ends up here so I pressed enter
Segmentation fault
[linux]$ ./a.out <--- started the shell back up
shell> ls | more | wc > output.txt <----- entered in the command with output redirection
In Child executing 0
First Child executing 0
In Child executing 1
Middle Child executing 1
In Child executing 2
Last Child executing 2
wc: >: No such file or directory
shell>
代码：
numOfCommands = numOfPipes + 1;
int pid = 0;
int leftpipe[2];
int rightpipe[2];
for (i = 0; i <= numOfPipes; i++) // loop for the pipes
{
if (numOfPipes > 0) {
pipe(rightpipe); // create right pipe
}
pid = fork();
if (pid > 0) //parent
{
if (i > 0) {
close(leftpipe[0]);
close(leftpipe[1]);
}
leftpipe[0] = rightpipe[0];
leftpipe[1] = rightpipe[1];
} else if (pid == 0) //child
{
fprintf(stdout, "In Child executing %d\n", i);
fflush(stdout);
if (i == 0 && in_red == 1) // first child and input redirection found
{
fprintf(stdout, "In Child input redir %d\n", i);
fflush(stdout);
close(0); //close stdin
fp = open(argv[2], O_RDWR | O_CREAT | O_APPEND, 0600);
dup2(fp, 0);
argv[1] = NULL; // set the file name to NULL
argv[2] = NULL; // set < to NULL
}
if (numOfPipes > 0) {
if (i == 0) { //first child
fprintf(stdout, "First Child executing %d\n", i);
fflush(stdout);
close(1); //close stdout
dup(rightpipe[1]); //make stdout=rightpipe
close(rightpipe[1]); //close write end of rightpipe
close(rightpipe[0]); //close read in of rightpipe
}
if (i > 0 && i < numOfPipes) { //middle child
fprintf(stdout, "Middle Child executing %d\n", i);
fflush(stdout);
close(0);
dup(leftpipe[0]);
close(leftpipe[0]);
close(leftpipe[1]);
close(1);
dup(rightpipe[1]);
close(rightpipe[1]);
close(rightpipe[0]);
}
if (i == numOfPipes) { //last child
fprintf(stdout, "Last Child executing %d\n", i);
fflush(stdout);
close(0);
dup(leftpipe[0]);
close(leftpipe[0]);
close(leftpipe[1]);
}
}
if (i == numOfPipes && out_red == 1) // output redirection found
{
close(1); // close stdout
fp = open(argv[sizeOfArgs - 1], O_RDWR | O_CREAT | O_APPEND,
0600);
dup2(fp, 1); // dup stdout to the file
argv[sizeOfArgs - 1] = NULL; // set the file name to null
argv[sizeOfArgs - 2] = NULL; // set > to null
}
indexOfCommands = startOfCommands[i]; //each index of startOfCommands holds the placement to the next command in argv
execvp(argv[indexOfCommands], argv + indexOfCommands);
}
}
wait(&pid, 0, 0);
close(fp); // close the file
}
}
管道正在正确执行，除了重定向，但由于某种原因，它将转向stdin而不是stdout然后导致分段错误，不知道为什么会这样。 任何帮助将不胜感激。