shell c中的输入输出重定向

Question

I implement a simple shell. I want to use input/ output redirection. I write some piece of code but my code doesn't work. here is my code :

Answer 1

You're duplicating the FD into FD 0, which is stdin . stdout is FD 1. You should also use dup2 , so you can specify explicitly which FD to assign to, and the macro that holds the FD.

dup2(fd, STDOUT_FILENO);

You should also change

if (*args[i] == '>')

to

if (strcmp(args[i], ">") == 0)

Otherwise it matches any argument that begins with > , even if it has other characters after it.

Answer 2

(get used writing %s\\n in your printf statements)

When your compiled program is called myshell, you will see the > when it is given as an argument:

./myshell arg1 arg2 ">" arg4

When you don't quote the > , the shell will take care of the redirection:

# Not what you want:
./myshell arg1 arg2 > arg4

would result in myshell being called with parameters arg1 and arg2, and the result of myshell will be redirected to arg4.

Answer 3

i think that u do not need asterisk* in your If condition. You want to to compare value of args[x] with a sign '>'.

In case it's not it, Can you write little more about the error which occurs?